If installed from dnf the files are in ~/.config/obs-studio/
If you installed with flatpak the files are in ~/.var/app/com.obsproject.Studio/config/obs-studio/
Every config you install for any flatpak app will have it’s files in a hidden folder in your user’s home folder.
.var/app/appropriate-app-name-here
If you use the flatpak for obs studio you can install a lot of plugins by using flatpak and they will install themselves in the appropriate place.
You can find a list of the ones you can install on https://flathub.org/apps/com.obsproject.Studio
At the bottom of that page go to the “add ons” tab.
Also, dont forget that if you have obs open and running while you install a plugin you have to restart obs in order for it to see the new plugin.