So we know Kang is going to be in Ant-Man and the Wasp: Quantumania. It's been rumored that the city we saw way off in the distance in the Quantum Realm near the end of Ant-Man and the Wasp is the TVA, and that explains why they can travel through time (they use the Quantum Realm). We don't know if magic works or doesn't work in the Quantum Realm, nor do we know if Infinity Stones work there - we know Scott didn't get snapped, but we don't know if that was just the randomness of the Snap, or because he was in the QR. We also don't know how Steve made it back from his alternate timeline to the prime timeline (see below); does the QR also allow movement between timelines? If so, that makes an even stronger case for the TVA to be located there.
I think it's more likely we'll get Kang next week, since the showrunners have said Loki has a more direct tie to future MCU films than the other two series. Do they do the reveal of Kang in this series? Or do they leave it for Ant-Man. Hard to say. But someone is definitely sitting at the end of time. The other theory being put out there is that's it's another Loki variant, but that seems too easy. Also remember that Ravanna is the Kang's lover, and be the one in charge of executing his plan.
So near as I can figure, technically, yes, she's a variant. Just like Thanos was in Endgame. However, TVA is (or was) charged with protecting the "Sacred Timeline" so whatever it is that meets the goals of the TVA is what they allow to stay. So, if moving back and forth in time like the Avengers did preserved the ultimate goal of the TVA, then they aren't variants, and they're allowed to do it.
So specific to Gamora, if the inclusion of the variant Gamora in the prime timeline doesn't hurt the TVA, then she gets to stay. Old Man Loki was allowed to stick around for ages on that planet because he didn't interact with anyone, and didn't cause any issues. As soon as he decided he wanted to get off that planet and go find Thor - well, that was enough that the TVA needed to prune him.
* Regarding Steve - Marvel has said that Steve went to an alternate timeline to live out a life with Peggy. And that has really bothered me, because I felt that he should have been moving in one timeline; it was too complicated to explain alternate timelines, etc. I really wanted there to be three Steve's alive during the Battle of New York (Battle of NY Steve, Steve from Endgame, and Old Steve). But considering how things are being explained in Loki, I'm leaning a lot more toward it being okay that Steve was in an alternate timeline. Just need the final loose end (imo) of "how did he get back to the prime timeline," which could be answered with the QR theory above.
Some additional commentary about this week's episode - Richard E. Grant was fantastic, and stole the show. Despite "Loki's never change," he showed us some real change. I loved his Old Loki, especially in the comic classic uniform. Loved all the Easter Eggs (Thanos Copter, Throg, Hi-C Ecto Cooler). The Loki fight was over-the-top fun and made me laugh out loud.
It's going to be a long week, waiting for this finale!