"The art of destruction" and "Being creative": These are the first levels of my "new" puzzle-making style that indeed started with Pit Lems, so they're perfect to demonstrate what this pack is all about. Even though Pit Lems does features X-of-everything levels - that was just me catering to community demands, or what I perceived as such - I think I've stated often enough that I dislike those. Instead, smaller puzzles where all the skills are accounted for are much more rewarding to me. There's a unique feeling of everything falling into place nicely when you use the last skill on the panel and the path to the exit is finished. A feeling that doesn't really occur for me when I look at the panel and think "...and I still had all deez!" 8)

Sometimes, I tend to think levels with small skill panels are too easy, or that it's too obvious where everything has to go, because of course it's much easier to maintain the overview and keep track of the skills on a smaller panel. But if even you didn't consider these first two levels easy, maybe this worry of mine is unwarranted. The idea of starting with small puzzles with tightly limited skill counts right away is something I took from Nessy's "Lemmings Migration": A pack that can easily stump you on its first couple of levels, but if it doesn't, or it only does for a short while, it's much more rewarding than many other larger packs out there. Lemmings Migration is still up there among my favourite packs, along with SubLems! It's also not very long, so give it a try if you haven't yet!

Athletic aesthetics: Yeah, this level is really pretty hard for its position. It's more of a thematic choice (1: destructive skills, 2: creative skills, 3: lethal skills, 4: athletic skills) to position it this early. If I were to re-create the pack today, I'd probably change its position - and I might do so after all, in Pit Lems Remastered. Since some levels from Paralems and Lemmicks are thrown into the mix for that, all the level positions change anyway. But for Pit Lems proper, at this stage I don't want to mess up people's replays by swapping around level positions. This can be precisely one of those early roadblocks, like in Lemmings Migration, that hit you early and out of nowhere.

Blocking all over the world: This level has been fixed a bunch of times and yet people still find ways to backroute it. I think you might have played an older version, though: I remember fixing the instance of this level on Lemmings World Tour (where it's part of the Professional rank, not actually of Encore, because it's such a well-known song, and a puzzle I quite like). But I'm pretty sure I hadn't fixed the Pit Lems original version yet.

Candyland Climber: This is one of the Lemmings-3D remakes mentioned in the starting post. The Cloner just adds some slight variation to it, and yes, that is indeed the most challenging part, because that's the part I added to it. In Lemmings 3D, this level is on the Fun rank, i.e. not supposed to be difficult at all.

All you need is time: Just supposed to introduce splitters, not made to be difficult at all.

You learn it, you earn it!: Funny, I actually thought this level was slightly easier than some of the preceding ones. I don't remember nin10doadict struggling with this one in particular during his Let's Play. Good to know - and nice to hear - that it was somewhat of a challenge for you, though!

I'm not quite sure what you mean in general when you say "more tricky than difficult". Does this refer to execution troubles, as opposed to puzzle troubles? Or are these just terms for subjectively different levels of a challenge?

Let's play Quidditch: This is the closest thing to a Paralems level that Pit Lems has (aside from maybe the level "Wasted talent", which is a fairer version of the ultimate-trolling level "Trust No 1" from Paralems). Because it's a book / movie reference, and the level justifies its presence through that, more so than through its mechanical challenge.

Na zdorovje Lem: This is a reference to a song by famous German comedian Otto Waalkes, "Nastrovje wom". "Na zdorovje" is often misunderstood to be Russian for "cheers"; it actually seems to be used more commonly to say "you're welcome". "Zdorovje" by itself just means "health". A Polish colleague of mine told me though that "na zdrowie" is indeed used to say "cheers" in Polish. So maybe, that German comedian Otto Waalkes was referring to something Polish instead of something Russian. Anyways, I've spelled it the Russian way. And believe it or not, somebody in the comments of nin10doadict's Let's Play actually got the reference! (IIRC, it was a German viewer as well, though. I doubt that many people outside the German-speaking countries know Otto Waalkes. But in turn, it's probably hard to find anyone in these countries who doesn't know him.)
PS: Because this is technically a song, the level also appears on the Encore rank of LWT. It's certainly one of the better puzzles in the Encore rank, while others were mainly just chosen for their title.

Check mate: nin10doadict considered this the hardest level of the pack, and it was the last one he solved. I placed it here because, once you get the main trick, due to the terrain shape, you can just keep repeating that trick to solve the level. But yes, this is one of the few X-of-everything levels I made that I actually still like. It goes to show how "iffy" terrain shapes can provide such a challenge in and of themselves that even having a plethora of skills, and the many degrees of freedom that go along with that, don't really help you all that much. I've certainly found some levels in Lemmings Plus I now that adhere to this principle. namida seems to be much better at creating this particular type of "any-way-you-want" level than I am.

Airborne aid: I think you're the first one not to be annoyed by this level. Slowfreeze for the win!

Glück auf (yes, that's how you actually spell it, but the NeoLemmix font doesn't cut it yet ): I'm pleasantly surprised to hear that apparently, you were able to pull off the Miner-cancel trick with Climbers.

Back during his Let's Play, I told nin10doadict this wasn't possible, and I even based a Lemmicks level from the Ephemeral rank, "Ignorance is bliss", on this belief. (You had to send up a Climber first, and then perform the Miner cancel trick with that lemming, which now no longer was a Climber, and I believed this was necessary to be able to do the Miner-cancel trick in the first place.)

Consequently, nin10doadict rightfully criticised that this level introduces the player to a corner-case of the Miner-cancel trick right away (=with Climbers), instead of to its "pure form". Because even though he knew about the trick, he wasn't able to pull it off with the Climbers. The intended solution doesn't use them either - it requires releasing the crowd into the tunnel so that one of the regular lemmings can perform the Miner-cancel trick. Of course, nin10doadict was able to do this - but only after I had told him that Climbers couldn't perform the trick.

Later on, while testing the penultimate level of the Legend rank of Lemmings World Tour, I found out that it is indeed possible for a Climber to perform the Miner-cancel trick. It just seems to be much more unlikely, because the Climber wastes time by "hugging" the end of the mine shaft, whereas a regular lemming turns around immediately.

That said, "Glück auf" technically isn't the first level to introduce the Miner-cancel trick: It's already part of the intended solution to "Doubling down". However, that level allowed for an alternative solution, which I wasn't aware of, but nin10doadict used. Hence, he could bypass the necessity to "learn" the Miner-cancel trick in its "standard form", so that when "Glück auf" hit him with the corner case of Climbers + Miner-cancel trick, it hit him out of nowhere.