I'm going to be going through
Wolves of Langston and, damn it, I feel like being a munchkin here.
So, give me your best suggestions. I already know about the pallid elf, thanks to DND Shorts on YouTube, but I'm looking for additional options here. (Also, since when are the Exandria races in the D&D Basic Rules? Wild!)
I don't know anything about that world. But if you are powergaming the best class is probably Wizard. You can do almost anything with a Wizard to include being a tank.
As far as best race, that is debatable.
There are flying races which are very good because they can fly, which solves a lot of problems, but these are weaker than other options if the flight is not going to be a big boon (and in some campaigns it is not). So in some campaigns something that can fly is flat best, in others they are not.
If flying is not a game changer, here are some other options:
Shaddar Kai - you get a bonus action you can use to teleport and get resistance to all damage. This is in addition to resistance to necrotic you get already.
Eladrin - Get a bonus action teleport which also imposes a condition on enemies (charmed or frightened). I have seen people play the other seasons that either allow teleporting two or damage enemies when you teleport, but although theese seem to be more popular, they are much less powerful IMO.
Goblin - Bonus action to hide and disengage. This is arguably the most powerful race for anything other than a Rogue. If you play a Goblin you should get proficiency in stealth through your class or background.
Bugbear - Extra reach and extra damage on the first round. This can be powerful, but it is really build specific. You want a very high initiative with a Bugbear.
Dhampir - Ability to walk on ceilings after 3rd level. Other than flight, this is going to anger DMs more than anything else, and it is usable where flight is not very usable. They also get 2 skills, 35 move and a bite they can use to cure themselves or give a bonus.
Kobold - If you are going into melee this is one of the most powerful classes because of Draconic cry which is a bonus action to give you and your allies advantage for a turn to everyone in 10 feet.
Mountain Dwarf - Medium Armor proficiency, several weapon proficiencies, and extra +1 compared to most races.