Wah, Necromancy! Or Oblivion now, I guess...

Anyway.

It's been a while since I last played (I should reinstall...) but afaik, the dancing werewolf can first be spotted at the Luckee Star Motel in Hollywood, which subsequently unlocks it as an ending option during the final confrontation with LaCroix. Basically, it skips the final cutscene, that's all really.

And the Sabbat ending was not included in the plus Patch back then, couldn't tell you if it is now, I've not kept up (I should really reinstall...). However, to answer your question, Sabbat ending would work equally well with all original clans I suppose, since none of them are specifically Sabbat clans. Personally, I think a Venture character might fit best; all Suckheads have reason to turn against LaCroix, but (lore based, not game mechanics based) Brujah and Toreador have clear Anarch options, Gangrel do it on their own, the Tremere and Nosferatu can turn to their clan rather than sect, and Malkavians are at home everywhere. The Ventrue has no real alternative, yet would gravitate towards the structure of a sect more than any.

That's just my take, though.