right now id expet PHB and nothing beyond that, especialy Volos and Xanthars sound like a bit of a stretch, Volos more so than Xanthars.
In terms of races: if you look at OS2, Larians approach to races is deep rather than wide, each race in OS2 had its own unique armor sets and weapons, its own unique animaitons and so on.
that doesnt lead itself to having 20+ races.
Then again, in DnD the vast majority of races is very simmilar to Humans.
From the PHB races only the Dragonborn and Tieflings are siginificantly different from Humans and even those are, essentialy, just humans with dragon heads or demon tails respectiveley
These are D&D races following 5e rules. Most of the work will be in creating the avatars of each race. No unique racial armour or anything like that. Limited racial feats in XGTE. Bladesinger wizard subclass only allows Elves and Half Elves (Shadar Kai are elves now, so they can be bladesinger which is just kind of weird), and battlerager barbarian subclass is Dwarf only. Other then those and the races traits there are no real races unique stuff.
So adding races in will be easier, plus the shear size of the team.
