Are there any difference between any% and 100% other than getting gold on the balloon touch challenges or is any% just 100% but you don't need to be perfect?

So far, that is the only difference. I've spent a lot of time trying to find anything that could speed it up beyond that, but haven't had much luck.

My best attempts at finding skips have all come from clipping OoB in the Overworld, and attempting sequence breaks. Unfortunately, the game is actually glitch-proofed pretty well, and many things that would have allowed for skips in the original N64 game have been fixed.

Also saw your TAS run of Ancient Lake. To my knowledge (I haven't spent much time with Time Trials) the fastest you can go in any vehicle is through using Taj or Wizpig (unlocked from beating Adventure and Adventure 2) with the Downforce 2 upgrade.

Yeah, I'm currently working on TASing Dino Domain for an any% TAS (which I wouldn't mind restarting since I have done a few optimisation mistakes, as well as not really knowing the strats) and this game seems hard to break. Hub world OOB might not matter much since you would still need all balloons, trophys and TT emblems to fight Wizpig 2, but OOBs in races could save some nice time.

Also can I have an explaination as to why Taj/Wizpig in Downforce 2 is faster than using Air?