Is there a way to have GTA5 installed twice, so i can play online, and start a different one with mods
@DamienDutch Yes, although not necessarily needed, it was discussed on this site recently, do a search. Tons of info on this site plus the internet in general. The site FAQ's are also a great resource for basic info.
Title of the post was for something else, but @a63nt-5m1th helps out the OP a little ways down in the thread to figure out how to switch between having two copies of gta5 if that is the way you choose to do it.
If you want to do it the easy way, there will be a file named dinput8.dll that basically makes it so mods will load. You can just temporarily rename that file to be able to play online safely without mods. I just rename it to 1dinput8.dll when I go online, and remove the 1 when I want play modded story mode.