Overall, my bet is that what Sven is indicating is likely how everything ties back to the situation with BG1 and BG2. It's pretty much a given that with how the various DoS games have eluded to, the protagonist(s) end up saving the world in some way, either becoming guardians (DOS) or setting someone up as the guardian (your protagonist, one of your companions, the antagonists - DOS 2), so I see the same kind of thing happening with BG3 (even in BG2:ToB you had the option to either let the antagonist take the power, keep the power for yourself, or let the power disperse). Same situation setup I see going here with BG3 where Larian re-hashes their typical endings from DOS 1 and/or 2.
There's still quite a few that WotC is talking about. Guallidurth, the city under the Calim desert, isn't much bigger than Menzo in 5E time frame (only about 50% larger), but was much larger than Menzo in the past. But both still pale in comparison to the city that is under Thay (can't find the name of it) which at it's height was well over 100k Drow and about 500k slaves (Menzo at it's largest was around 20k Drow and 60k to 70k slaves and Guallidurth was around 80k, not sure if that's combined or just drow).
And the other two "Drow" groups I really wouldn't consider Drow as the one is the Starlight Elves (northern group) and I can't remember what the southern one is, but the southern one is closer to that of Green/Wild Elves (which the Drow were originally Green Elves) and are more like Wood Elves in mentality. The Lolthsword Drow are by far the largest group that remains of the "Green" Elves.
Drow being originally Green Elves is not exactly 100% canon. If you take the Lady Penitent series to heart, then yeah maybe you could interpret that way since they have both been describe in similar physical terms IIRC. But Drow/Green Elves being their own separate subspecies distinct from the Green Elves has ample precedence before and after that series. Plus the whole 'Curse of Ham' thing with the literal blood taint that particular series decided to run with made lots of people uncomfortable at the time and absolutely would not fly today.
Have WOTC talked about any non-Menzo cities post the whole Udadrow/Aevendrow/Lorendrow debacle? Their new history/definition of the drow leaves very little wiggle room to interpret vast sprawling underdark cityscapes spread around Toril. The wording they use makes it clear that Menzo=udadrow and that the Lorendrow/Aevendrow are the 'good' equivalents to that city state. Note stuff like the Lorendrow being an open surface-dwelling city in southern Faerun that doesn't try to hide but is safe from the Spider Queen because of it's *geographical distance* from Menzoberanzan. Which makes no damn sense if cities like Guallidurth or the nation of Dambrath were canon, because Southern Faerun is(was) an absolute bastion of ancient and powerful drow holdings. It's also 100% clear in the new canon that the Lolth-worshipping drow originate from Menzo, and it was Lolth's fault for tricking them underground (specifically to found Menzo) rather than the Crown Wars origin. Menzo is only a few thousand years old btw, which mean drow as we know them are basically a blip on the radar in terms of FR history now.
Thing is, they're still keeping a fair amount of Greenwood's world information. Afterall, they backtracked on the lore and happenings of 4E (killing all the Drow gods off except for Lolth and Ghaunaduar since it's more than a Drow god) which lends a lot to keeping various information found in the *Drow of the Underdark* from both 2E and 3E/3.5E. If you go back through that information, which WotC hasn't completely gone off the deep end like Disney did, can still go back on the old information and pull it forward and that old information does point specifically at Green Elves becoming the Drow when they were fighting against the Gold Elves when the Gold Elves almost destroyed some of the other Elven sub-groups. In order to fight back, the Green Elves turned to Lolth and demons to fight back against the Gold Elves even though the Seldarine also were fighting against the Gold Elves as well and assisting the other Elven sub-groups. Because of the tactics of the Green Elves and the overall destruction that was happening to the Elves overall and the fact that the Gold Elves were willing to return to the Seldarine even though it was there actions that lead to the war between all the Elves that the Seldarine then cursed the Green Elves turning them into the Drow and left the Drow with only the option of continuing to follow Lolth and thus went underground into the Underdark.
The other thing to realize is that WotC with 5E have really limited the scope of Toril that they actually talk about with it centering around the Sword Coast area of Faerun and not really dealing with other areas. It's known that there's a very large above ground Drow populus out in the Dalelands. Though, because WotC is concentrating on the Sword Coast, that isn't brought up in 5E much. WotC would rather try to push in MtG settings into D&D instead of using the existing world settings they have access to. So I wouldn't say that it's really WotC changing things around a lot, but instead ignoring what is out there already (this is why if you go to *Dungeon Master's Guild*, you'll find a lot of written material for 5E from Ed Greenwood and others for the Faerun setting outside of the situation in the Sword Coast).
