I had a go at this challenge using DOSBOX, and the only one that really gave me fits was Mayhem 15. The digger pits at the beginning required some quick transitions on opposite sides of the level. I got most of the others pretty quickly. I don't have any videos, but I thought I'd share my number of attempts for each level and describe a few of my own bloopers:
Wicked 4: 4 tries for 98%. My second attempt "failed" while I was trying to rescue the last group, but the funny part is I had already saved enough lemmings from the other hatches to pass the level, so I had to reenter the level code to try again!
Havoc 9: First try
Mayhem 11: 3 tries. My first attempt goes in the blooper hall-of-fame: I clicked on the first lemming as he approached the end of the platform, only to watch him continue to walk right off the edge. I then looked at my skill panel and saw that I had never switched to Digger! In all honesty, though, I found this one to be a piece of cake if you set the release rate to 50-55 and just assign diggers to every other lemming.
Mayhem 15: 11 tries for 100% (in under 2 minutes, to satisfy Amiga requirements). My most comical failure was when I tried to quickly switch from Builder to Digger, and ended up pausing by mistake, as that icon is right next to the digger icon.
Mayhem 4: First try (100%)
Mayhem 21: First try, and yes I did make the first lemming a Climber. After that he only needs to be assigned four skills, and only one of those assignments needed to be made as a lemming was coming out of the hatch. Fortunately I saw this coming and was prepared for it.
Mayhem 20: Second try (the first try failed when I assigned the final miner too late and he mined under the exit instead of through the top of the bridge.)
Havoc 7: 5 tries for 100%. The successful attempt almost resulted in a comical failure when I nearly forgot to assign climbers to the group that needed to climb to the exit. Fortunately I caught it just in time and managed to spam-click on everyone.
Havoc 12: 2 tries for 100%. I had a total mental lapse right off the bat in my first attempt, forgetting that the first lemming cannot simply drop down to the pedestal; he needs to build there!
Havoc 20: I saved 85% on the first try. If not for two mistimed bombers, I would have had the maximum 88%. It helped that I had played this level recently and remembered exactly where the first bomber had to be set to keep everyone away from the lizard trap.