Is it possible to install mods in an online game without causing conflicts?

Is there any way to safely install mods I find on the internet without affecting anything in the game? Like, only use them in online and keep offline with nothing?

I don’t know if I’m being clear, but for example, I have GTA V and sometimes I play online mode. But I downloaded several mods to have a favela, to have that “Back to the Future” car and so on. I’d like to know if it would be safe to install them and still be able to enter GTA V Online normally? With no risk of a permanent ban and so on? Or do I need to uninstall everything before launching the game?