As question goes what good race for Balance druid ?
The consensus over the past several expansions has been Night Elf – both for PvP (primarily Arena) and PvE (primarily Mythic+ Keystone dungeons). I suppose you could play Tauren to Warstomp-Cyclone some arena setups, For Raiding – Troll for the Haste or even Worgen for the extra mobility (though we’ve got plenty of that). Kul Tiran has a fun knock for some battlegrounds as well… All in all, you should probably play whichever race you enjoy the most in terms of models, customization, animations, transmog silhouettes and lore… But if you really want to min/max, the answer is almost definitely Night Elf. Though, I’d argue (from recently changing back and forth…) that Shadowmeld (Night Elf active racial) is simply too beneficial to pass on in general, even if just for the open world. Being able to disengage from any situation, be it a big pack of mobs or an unfavourable world PvP clash… and fly away, is a huge Druid advantage as it has been since its modern iteration.
Enjoy Boomy! The coolest spec in the galaxy