Here are more details on differences between the arcade levels and their Amiga/DOS counterpart. (Warning: long post ahead)
(Note: there might be some miscellaneous changes to decorative terrain that I might have missed here and there, where they are totally out of the way of normal solutions. For the most part though the levels are pretty accurate straight ports of the original, so I expect such changes if any to be rare. Level area width seems same as original, given levels like "Rendezvous at the Mountain" can be ported as-is.)
First let's start with the few that are meaningfully different:
16. Better Look Both Ways (Crankshaft)
This level is turned into the first 2-entrance level in the game. The exit is moved two sections over left from where it used to be, and the section where the exit used to be is the other entrance. Also 10 bashers are added to the skillset compared to DOS Crankshaft (so now 10 of everything). No terrain changes.
18. Look Before You Leap (How Do I Dig Up The Way?)
Another conversion to 2-entrance level. The second entrance is of course on the right side. The exit is moved to the valley in the middle just above the water, on an extra platform at the middle of the lake, with a gap each on both its left and right sides that you need to build over. No other terrain nor skillset changes.
35. But How Do I Dig Up? (King of the Castle)
Um, just see attached screenshot for the terrain and skillset changes. Basically made the level somewhat more like "The Boiler Room", though I guess you can also take an outside route as well.
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Now the other levels with more minor terrain or object changes. In many cases the changes seem to specifically reduce the amount of building needed.
[unless otherwise noted, assume no terrain nor skillset changes. Unlike DOS version, the water/lava/acid etc. you see in Amiga version are all kept in the arcade port.]
10. Izzie Wizzie lemmings get busy: entrance moved two over to the right, to the 3rd "bowl" from the left, with lemmings landing on left side of bowl rather than in its middle.
11. The ascending pillar scenario: entrance moved to middle (4th) pillar. 10 blockers and 10 bombers added to skillset.
19. Every Lemming for himself: exit moved two over to the left, so you only need to build over 1 gap instead of 3. Skillset changed to 5 of each skill except for miners and diggers (still none for those two).
22. Down, along, up. In that order: exit moved down to the bottom-most of the 5 floating platform, the other 4 floating platforms are removed.
39. Last one out is a rotten egg: the one-way wall (just the object, not the wall terrain itself) is removed, so you can mine through it from the left if you want. (one-way walls do exist in this port so it's not just a general removal of one-way walls.)
40. Curse of the Pharaohs: the pyramid has some weird gaps, almost makes me wonder if they are really intended or not. See attached screenshot.
42. The Fast Food Kitchen: The two entrances are both moved closer to the exit, specifically over to the other side of the obstacles you'd normally have to bash or otherwise trailblaze through.
46. Livin' On The Edge: The exit is moved two over to the left so that you only have to build across 4 gaps instead of 6. The pillar to the right of the one where the exit is now moved to, is removed, as are the bricks (but not the other terrain) where the exit used to sit.
47. Upsidedown World: The one-way wall object (but not the terrain) near the exit is removed.
48. Mary Poppin's land: the uphill and steel column is followed immediately on the right by an added symmetric downhill, instead of the usual sheer vertical drop. See attached screenshot.
51. Steel Works: the exit is moved to sit on the floating steel block at the middle of the lake.
52. The Boiler Room: miscellaneous terrain changes near the exit area, but doesn't really affect the solution. See attached screenshot.
54. Pillars of Hercules: the two exits are placed at floor level rather than on top of tall pillars. The two tall pillars with the exits are removed.
63. The Far Side: exit is moved to ground level rather than sitting on the row of 4 steels blocks, which are removed.
66. Save Me: the steel platforms at the exit area are much more offset from each other, so you don't need to do the build+block trick there, you can just block. 6 bombers are added to skillset and number of builders increased to 40.
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Finally, RR- and/or skillset-only changes (again, nothing to write home about; generally you get more than the original version):
(training levels): release rates [RR] are changed to 80 where they used to be 50, except for the builder level where it is changed to 60. The miner+climber level also has RR changed to 60. (However, see later remark on how the arcade version's RR value translates differently to spawn interval. So the RR changes are actually not as radical as it might sound, in fact it seems more like it's done to keep things similar to the spawn intervals used in the original versions. That said, of the other 59 levels, only 4 have their RR values changed from the original.)
"Just dig!" has 10 bashers and 10 miners added to the skillset in addition to the usual 10 diggers.
miner+climber level has number of climbers increased to 25 to match every level having 25 lemmings in the arcade port. Similarly, the floater level now has 30 floaters.
Tribute to M.C. Escher: skillset changed to 5 climbers, 5 floaters, 5 bombers, 5 blockers, 10 builders and 5 bashers.
Tightrope City: number of builders increased from 3 to 5 (so 5 of each skill).
We all fall down: RR changed to 60. Interestingly number of diggers stay at 20, even though level has 25 lemmings.
Follow the leader: RR changed to 30, number of builders increased from 7 to 10.
Poles Apart: skillset changed to 4 climbers, no floaters, 2 bombers, 2 blockers, 6 builders, 6 bashers and 4 diggers.
Just a Minute: skillset changed to 80(!) climbers, 80 floaters, and 10 each of the other six skills.
The Steel Mines of Kessel: 1 basher added to skillset. Like the Amiga/Mac etc. versions and unlike DOS version, you get 10 each (instead of 20 each as in DOS) of bombers, blockers and builders.
Just a Minute (Part Two): the 5 bombers in the original skillset are removed.
Cascade: skillset changed to 1 climber, 30 floaters, 5 bombers, 2 blockers, 10 builders, 2 bashers, 2 miners and 5 diggers.
If at first you don't succeed: skillset changed to 10 of each skill.
Compression Method 1: skillset changed to 2 floaters, 5 bombers, 5 blockers, 5 builders, 10 bashers and 4 diggers.
The Crossroads: number of bashers reduced from 20 to 10.
The Great Lemming Caper: skillset changed to 2 of each skill.
With a twist of lemming please: number of builders increased from 4 to 5.
All or Nothing: skillset changed to 10 bombers, 10 builders and 10 bashers.
POOR WEE CREATURES: RR changed to 50, no skillset change.
Who Used All The Blockers? (From the Boundary Line): RR changed to 70, no skillset change.
Triple Trouble: skillset changed to 20 of each skill. Also, the pattern in which lemmings come out of the 3 entrances is ABCABC... rather than ABCBABCB... of the original.
Mind the step: skillset changed to 10 bombers, 10 blockers, 30 builders, 30 bashers and 30 diggers.
[edit: one more thing below]
Rendezvous at the Mountain has no apparent terrain, object nor skillset changes, but the fall from the left entrance is fatal in the arcade port. Also on the right side, it seems the level area's right boundary is located more to the left on this port, so the lemmings can't fall off on the right end in this level, instead they hit the invisible boundary and do a glitchy turnaround (more details in another post).
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Miscellaneous remarks:
In this arcade port it seems generally objects cannot be made to be displayed behind terrain. In most cases this just results in ugly looking water where it meets terrain that normally covers up the water edges. Then again, this also causes "Lost Something?" to be pointless due to the exit not properly hidden from view, and similarly the traps in "Compression Method 1" are visible at all times (though one might argue that's an improvement).
RR in the original game works as follows: at RR 99 the spawn interval (distance between consecutive lemmings in pixels) is 4, then for every decrease of 2 in RR, the spawn interval increases by 1.
RR in the arcade port works instead as follows: at RR 99 the spawn interval is 2, but then for every decrease of just 1 in RR, the spawn interval increases by 1.
So while at RR 99 the lemmings are packed twice as dense as the original, in other levels where the RR value is kept same as original, the lemmings are actually coming out almost twice as slow as original.