I would like to replay VtM:B (in preparation for its sequel!) and am wondering what are your recommended mods to apply? I played vanilla last time round (a few years ago). I am aware of "The Final Nights" and "Clan Quest Mod", but could only find old reviews from several years ago. Has anyone played them recently? Are they good? Any others worth recommending?

(I also have never played as a Malkavian in the standard campaign, so I guess I need to try that also!)

In that case I would suggest to play Malkavian plus patch first and then CQM or TFN...

Are TFN and CQM new quests added to the original campaign (i.e. you still have the same main plotline), or are they completely new stories from beginning to end?

TFN is pretty much the same storie but with different clans and one or two new side missions. CQM is with the old clans but has several new side missions and since the 4.0 version a new hub and a new Sabbat storyline which deviates quite a bit from the original one!

Thanks! So I can play Clan Quest Mod as Malkavian, kill two birds with one stone?

Yes. But for now you will miss most of the new plus patch content...

Is "Antitribu" a worthwhile mod, or better to ignore it? Looking at moddb it hasn't been updated since 2016, is it in a usable state, compatible with the GOG version?

I believe the latest version of Antitribu has the mod loader, so it is compatible with the gog version of bloodlines, and there shouldn't be any gamebreaking bugs either.
As for the question if you should play it, well the opinions differ. Many people like it. Personally I have uninstalled it just after getting to Hollywood. IMO there are too many unexplained fights, and what they have done to the Ocean House and Grout's mansion is just terrible.

Ok, given all the buzz and fuss about the newly-announced Vampire game, I'm willing to give the first one a try, so which mods (mainly in the categories "bugfixing", "cut-content" and "graphics") do I have to use to fully appreciate the game? I'm not looking for new clans or new quests at this moment.

Unofficial Patch has all your bugfixing and cut-content needs covered.... As for graphics, no idea. It's a 2004 game that looks like a 2004 game, which was fine for me, YMMV.

Edit: Looks like X20 Mod is a textures-only graphical overhaul that works nicely with Unofficial Patch.

By any chance, does the GOG's VtM:B have any mods applied to it?

It has a "basic" version of the Unofficial Patch pre-applied (without any "plus" content).

Ok, thank you for your help :)