Where can you learn the mechanics of this game? Like what are the strategies to go fast? I've looked all over this page and google and can't find anything

here are my fave bikes for each weight class
small (worst): quacker
medium: mach bike
large: bowser bike/ flame runner

also if you want the easiest ultra shortcut the grumble volcano one was the first i learned

idk if thats realy what he is asking but tbh i would say warios gold mine voiding is quite easier (without the pipe boing)

Ask around in Time Trial discords

ArcIntel is a great YouTube channel if you're trying to learn shortcuts. They're short and easy to follow most of the time. (Link: https://www.youtube.com/c/ArcIntel)

You could also watch other peoples runs of courses, see what they do, and incorporate that into your own runs