I have around 300 mod subscriptions on my Steam Workshop profile, most of them are costume and badge mods and I want to see if there's any way I could disable the mods for a while so I don't cheat on the speedrun. Thanks!

If you're on 2.1 you won't have to worry about that since 2.1 doesn't have workshop support. If you're on a newer version you can scroll all the way to the bottom of game settings and check the disable mods setting and relaunch and you should be good.