So I have a small issue with RageHook.

I renamed the folder to Grand Theft Auto V SP - so that I have a dedicated multiplayer game files in the original folder, but as soon as I start RageHook it crashes saying that either the system is slow or insufficient permissions. I renamed the folder back to Grand Theft Auto V and it worked, but the problem is that STEAM always launches the modded version and I can't launch the vanilla one if it's not in the folder with the original name.

Is there a way to somehow make RageHook launch the game from a different folder rather than the vanilla one that Steam creates for you?

This is normal. 

 

Your game folder needs to be called Grand Theft Auto V. You'll have to rename your vanilla/mulitplayer folder "Grand Theft Auto V MP"  and have your modded one Grand Theft Auto V. then rename the folders each time you want to use that particular folder (like renaming the MP to Grand Theft Auto V and renaming your modded folder to something else when you want to play online)