One of the more interesting monsters to me has always been the Draegloth. There was a playable version back in 3.5, and was curious if anyone had ideas how to take elements from that as inspiration, and the newly released monster version in Volo's, as a guide for making a playable 5e version. It would obviously be severely weakened compared to its monster counterpart, and be medium sized instead of large (maybe having that trait that gives it higher carry, push, pull and drag capacity like Goliaths have). 

D&D 5e and playable monsters have had a history; take a look at the Centaur and Minotaur UA. The biggest addition from this UA was the trait Hybrid Nature that has allowed these monstrosities to be humanoids without breaking the rules already presented.

Instead of creating a new race, I see a very easy way to add it to an existing race: a tiefling variant. You replace the intelligence with strength, Infernal Legacy with Drow Magic. And you give Fey Ancestry, Powerful Build, and perhaps Hybrid Nature.

Why tieflings? Tieflings get racial feats in XGtE that compliment Draegloth features perfectly.

That is already some amazing advice. I'd drop hybrid nature though since they are closer to demons and don't really have that half and half aspect minotaurs and centaurs have as beasts. Hybrid Nature focuses on the idea that they're half animal, not half human. And split between their tops and bottoms, and not blended features like a Tabaxi or Kenku are. 
But taking bits and pieces from Tiefling and Drow is an excellent idea. 
Instead of Hybrid Nature, perhaps something pertaining to their vestigial arms, and larger upper arms? Like "Long Reach" like bugbears have while having their lower arms able to hold things, but not really be useful for wielding weapons or for spellcasting in combat (yes, I know they use all four arms in combat in the novels, but this is a less monstrous, playable version of the Draegloth, so we can say the lower arms are too underdeveloped).
For flavor purposes, you can say the hands can be used for ritual casting when there isn't a lot of frantic movement like there is in combat. 

Here's the first draft. A lot of it is kept to be close to a tiefling, while adding watered down traits from the monster block. 

https://www.dndbeyond.com/characters/subraces/34158-draegloth

Hybrid Nature actually focuses more on the fact that centaurs and minotaurs have the monstrosity type in the monster manual. Draegloths are in a similar bind as they are a fiend. You could give them Hybrid Nature and simply replace monstrosity with fiend and be set.

Edit: Taking a quick glance at the race, it seems fine. Long reach might be one thing too many. Also, remember to tooltip spells. And make sure you don't lift text straight from the draegloth description as that is copyrighted.