Can i install mods in an already existing world?

I am playing for the first time subanutica with mods, playing the Return of the Ancients.

And after looking for more mods i discovered the Beluga or ATLAS one, and i really wanna try it, maybe the Mantis sub too, and some quality ones.

Does installing mods messes a already used world? And does Return of the Ancients bug with those mods?