I've seen a video on how to setup your game but there is so much stuff you have to download. what is actually required to speedrun(1.16.1)?

load up minecraft 1.16.1 and start playing, thats all you need to do. you can install performance mods and practice maps but nothing is required besides the game itself.

I agree, you technically need no mod as long as your computer is able to run the game just fine. I would however recommend to at least get the SpeedrunIGT mod by RedLime, because it makes it very easy to know your time. I think (but I could be wrong) that you can still upload a run that doesn't show the in game time, but I am sure moderators would like you much more if you show the in game time in the recording of your run :)