I’m probably going to do some vs mode runs as soon as I figure out a poopcam setup

When you get the last star of a level you wait for yoshi (or whoever youre playing as) to do his little dance and then pause the game and exit the course. The run ends when you touch the last star of the 4th course like in any 100%.

Can there be a singleplayer vs mode on the level leaderboard? Like you collect all the stars in the course in the fastest time possible and maybe a vs mode 100% where you do all 4 courses.

no, but there are a lot of other glitches in this game