If we talk about races that have a rich lore and presence and didn't make the transition from Legion to BFA it's the Vrykuls.
I really like them, both visually and from cultural prospective, not to emntion they could legit be the (probably only as of right now) allied race that could be a DK (and what a DK i might add).
As for playable classes as a whole i'd say this (i'll give explanations):
DK: YEs, for obvious reasons
DH: No
Warrior: OBVIOUSLY
Mage: Yes
Priest: Yes
Shaman: Yes
Druid: YES! this is a bit more controversial, but given how deeply the Vrykuls are connected with their territory and nature in general it would be a good match, and hell, i took quests from a talking tree in stromheim!
Monk: Yes! Can't have viking race without beer, plus they are a good match for a heremit type of dude
Rogue: ehmmmm YES!. It is controversial but we saw vrukuls be very shady guys at points as well, AND they are master Pirates giving a lot of credibility to an outlaw vrykul rogue at least
Paladin: Yes. A "different" type of paladin if you want, but just go in the halls of valor and you'll have paladin vibes all over the place.
Hunter: Yes
SO yes imo Vrykuls could be the most versatile race added to the game to date.
But... what faction?!? Horde or ally?
Okay so there are some strong point in favors of both.
FOr Alliance, they are the race that the humans came from, so they may find again a new spirit of collaboration between the modern humans and their ancestors, and from a visual point of view, the alliance having a proper humanoid giant race fits strong in their ranks, as in almsot every fantasy dwarves, giant and humans share the same world.
BUT!!
FOr Horde: We cannot deny that probably the view of the world of the horde fits the cultural way of life of the crykuls at 200%. They sshare the same pride and honor in battle as the Orcs if not more, so they would get along no problem in a war scenario. They have very shamanistic traditions and that also goes just as well with the horde in general, since both orcs, trolls and taurens havestrong spiritual traditions.
So for this reasons i would honestly put them HORDE, even with some strong points in favor of alliance