Were I on Larian's shoes I would make Tav some sort of exiled planer regardless of race. If I remember correctly, all the races have representation in sigil, so just make small background about the MC doing something to piss off the lady of pain, but leave it vauge. Since you're not going back to sigil in this game you are basically a clean slate.

Larian's Biggest Oversight, what to do about it, and My personal review of BG3 EA
"74.85% of you stood with the Tieflings, and 25.15% of you sided with Minthara. Good outweighs evil, it seems."