I really must thank you for this one.
As much as I liked Story Mode, it was too small a sampler for me to really get a hang of several of the new mechanics to the point where I would be comfortable with levels that focused on them. I still don't have the hang of Twisters, the 3DW builder/hammer takes a ton of adjustment because it has a wind-up time before you can dash, I only really understood crates today after making a level around them (which will probably be tough on people unused to crates), and coming into this I certainly didn't have any grip at all on the cat suit. Some of the 3DW mechanics play so differently here than they do in 3DW proper that it's like picking up a whole Mario style without having an official, full-sized Nintendo game around as a reference point. I think the highest compliment I can pay your level, then, is that by the end of it, I felt like I totally understood how Cat Mario works in this game. (In Story Mode I was instinctively diving everywhere and never consistently understood how to lean into a wall climb to distinguish it from a wall jump.)
I said this already in a course comment, but I was very relieved to get far enough in the level to confirm that yes, the coins are plentiful and I was allowed to be a bit sloppy in places and still reach 100 easily. At first, when I saw the looping structure of the pipes on the first screen, I had some mild trepidation that I'd have to loop back multiple times to clean up anything I missed. (On the other hand, the in-game clear condition was clear about not specifying "all".)
You'll notice that a ton of death markers are clustered right at the start. This would be because the very first thing you test is the long jump, which threw me off a bit because I thought this was a cat course; it took me a moment to process that something else entirely was going on. I didn't have a problem with it (one of the great design landmarks for me is the first screen in DKCTF's Bopopolis, which is basically there to say, "Look, you'd better learn this game's bounce timing now because if you don't know it, you're not going to survive the rest"), but it did seem strange that this is the one and only place where you need the long jump, and I'm sure a lot of players will wipe out right there, wondering why nothing in the guide concerning cats is of any help. (Reading your description, I guess it wasn't actually necessary—but with the lava rising fast, and no indication at that point that there is so much wiggle room with the coin supply, you can bet that players will throw themselves at the coins and miss.)
Anyway, this was a great training ground, and it's the kind of course that would probably have a much higher clear rate with a mature player base that already has the hang of the controls across all styles, the way that handling shellmets and Clown Cars became second-nature after a while in SMM1.