Yeah, you don't think it's too much just to get most of a second background? Thanks for all your input on this, Garren!
It's no problem really. And no I think the balance will be fine. While true in most cases you will grab 3 proficiencies from the ability the fact that they are set in stone rather then the flexible choices Half-Elves get keeps them fair. In most cases they will have the same Skill proficiencies as a H-Elf for all intents and purposes.
I don't think elves are actually considered fey in this edition. Would it break anything to make them fey and deva celestial?
All the player races are humanoid this time around though honestly Creature Type means far less then it did in previous editions. Only situation that could arise by having Deva be Celestials and Elves be Fey is if your players get cute and say 'my deva is a celestial, not a humanoid, and is therefore immune to Charm Person' - which is technically correct as far as RAW goes. You could easily just hand-wave that though; Planescape did the same thing for all it's weird celestial/fiend/elemental races so there is precedent for it.
As for your sub-races I'd need a little more info on what exactly the differences are to make any fluff recommendations. Based purely on mechanics though;
WakulimaLooks good to me. Advantage on Knowledge checks is really useful without hitting the same issue you get from advantage on physical or social skills - sees enough play and use without just flat making you better then your associates. Don't foresee any balance issues here.
WapiganiI'd avoid v2 just because at that point your average Deva is going to have 6-7 skill proficiencies regardless of class. That isn't terrible it's just getting a little redundant - given that 5 of them will be set in stone your going to have skills overlapping at that point. v1 and v2 honestly don't have enough difference for me; Survival is basically Tracking, Foraging and Hazard-Spotting. Granting advantage to two but not the third seems like it would cause more issues then it would solve - especially when players want to know what they can follow an owlbears tracks but not notice which of two caves it's living in.
WasafiriI'm guessing these guys are outriders or cavalry or some such? Anyway v2 has the same issue I mentioned above. Of them all I prefer the 'prof. bonus on Con saves vs forced marches' thing the most. Advantage is troublesome when applied to physical skills and, if the player is going to pick this sub-race with the intention of being mounted, will probably pick a class or background which grants animal handling anyway.