Check out my levels.
https://supermariomakerbookmark.nintendo.net/profile/Wariofan192?type=posted

I tried a couple of your levels, here´s what I think about them.

fun underwater level is the best one I tried. I think it´s an inspired level design with several nice nooks and crannies. Poor Yoshi seems lost at the end. Indeed a fun water level!

quick course ended up pretty hard, I had to try a couple of times before I was able to make it past the Chain Chomps and Twomps. I had to reach the goal using damage invincibility.

traditional Mario course is pretty untraditional. I think it would benefit from more planning at the end, it felt like springs and platforms were placed at random.

ice course is too hard for me, I die very early unfortunatly.

bowser jr castle was exciting, the first day I tried it I just couldn´t understand how to get past the block wall. Today I saw the flame spitting cannon and it felt good to clear the course!