Played through this episode, and I really enjoyed it. The collectathon structure and the odyssey vibe you bring to this episode are very apparent, with the moon collecting ring being a nice touch when entering each smb2 door. Even the small platforming pipes and some of the overly easy doors in worlds were pleasant and brought the odyssey vibe you were shooting for. 100%ing this episode wasn't that bad either. Whether it was your intention or not, I always felt motivated to complete each world before moving on to the next and I only found my struggling a couple times throughout playing.
Most of the worlds were also well-established and never overstay their welcome. That being said I felt like your smaller worlds such as Greed Street and Polluted Pier were missed out potential; these two worlds in particular felt like they'd be the most unique before entering aside from Sazaku Village, so I was disappointed that there wasn't more to them. Greed Street would have been amazing with a couple more minigames and especially more platforming in the main area on way to the boss; you used an awesome tileset too so I was honestly expecting there to be more casino like obstacles and what not. Polluted Pier might arguably be more guilty of this as a lot of the world's elements are just from a castle level (thwomps, grinders, lava) that happen to have the haunted pier aesthetic. Basically it's a similar complaint I have with odyssey itself with the Cloud and Ruined Kingdom's being wasted potential, but at the very least your smaller worlds have more stuff to do in them.
On the contrary though your best levels are really enjoyable. Sazaku village having the similar vibe to Bowser's castle while throwing your own unique twist to it was nice, I loved Whimsical Wasteland even though I would've loved to have more snow world representation, and Double Tower Plant was both enjoyable and challenging to go through. The other worlds I didn't mention are also really fun, and there really are no bad levels in this episode that I dreaded playing through. The bonus levels at the end were a nice touch too, though Cheesy Desert and Dark Hole had potential to have more stars to them. The unique gimmicks in every world were a breath of fresh air as well.
The boss fights in this game are well-thought out, and I love what you did with each to make it more unique than the last since most bosses replaced the Mother Brain NPC. It's a good example of being creative with limited resources. The final boss fight itself was fun to play through, but I did get frustrated with how buggy the giant bowser sequence would get at times as I felt some of my deaths seemed unfair.
Overall though this is a very well made episode that I thoroughly enjoyed through and through. While I think some of the platforming pipes in later worlds could have had more to them and while the overworld could have been a little bit more interesting, I think the big point here is that this episode left me wanting more. I can definitely see myself replaying this episode in the future, and I hope you're considering cooking up a sequel for this episode too. So great job with this episode, I hope to see more, and I might be looking at your other finished and upcoming projects fairly soon. (Also sorry I'm around 2 years behind since this came out)
Check out my current project, Super Mario Country: