Cool, much thanks.
Most mods for the game require the UP to work, I believe, but some may not work with the newer versions of the patch so, if you try one of those, it may not work. There may be a few out there designed around the "True Patch Gold" (TPG) and those may not work too.
I don't know of any mods that use the "true" patch and the mods that are built on the unofficial patch have the needed version included.
Afaik, Antitribu, Camarilla Edition in the latest version and Clan Quest already support the mod loader, so you can just install them on the GOG version without trouble.
The Final Nights and Companion Mod don't use the mod loader. Here your best bet is to install the mod in a temp directory, rename the /vampire folder of the mod, copy the renamed /vampire folder in the bloodlines root directory and create a launch icon.