This is my first time speedrunning, can anyone tell me some mods I can use on scarab to practice PoP?

Also, how would i do path of pain again if ive already completed it on my main save, and mods arent allowed in PoP speedruns???

I would recommend not using scarab at all. QoL (that does unlock infinite PoP on any save) messes with room transitions, namely it removes the 0,56 delay when entering a room. PoP is very cycle dependant, and that would throw you off. You will have to relearn pretty much all the rooms (I speak from experience here) when transitioning to what is actually allowed in the runs - mini savestates mod, as mentioned in category rules. So my advice - install mini savestates on a clean game with no mods, learn how to reset runs (for that you will need a save that didnt beat PoP yet) and enjoy practicing. That way, when you git gud, you could immediately submit footage of a run and it will be legit. Good luck!

how do i install mini savestates? where is that found?

Go to resource page for HK speedrunning, found under "resources" on speedrun com, right next to guides and forums. Its the first link. There, scroll down to find MiniSavestates. Download an archive for the game version you use (check in the main menu in game if unsure, but most likely 1.5.78). Then unzip it to Hollow Knight\Hollow Knight_Data\Managed. Saving original Assembly-CSharp.dll is useful to easily revert the game back to unmodded, if you want to run different categories later. Default hotkey to create a savestate is F2, and to load a created savestate - F1. Create a savestate right after a breakable wall before PoP, then revert to that state with F1 after each failed attempt. Hope that helps!