Custom races are considerably easy to make the races game breaking, but the base nalakim also seem considerably overpowered at present.  So just curious if more tweaks are coming to the game in future?  

Probably not, the game's pretty much done at this point. There's a final patch (currently as prepatch preview) that need some final work and push as official, and that's about it.

Different races/factions are quite asymmetric, is a highlight of the endless 4x series, but yeah there's balancing concerns regarding a competitive focus (IE: Multiplayer).

If you want a more balanced experience, you have ESG mod, that aims to bring the game on a more fair approach, also adds tons of cool stuff. But you'll lose on the asymmetric approach.

Also I think the game needs a bit more love in some of the mechanics and late-game buildings. Inflation is not in a good place, invasion/siege also doesn't feel good as a conquest mechanic, many T4-T5 buildings are all over the place, some are great other near useless. Faction-specific T4 unique buildings generally are not worth the tech slot, etc.

And Military research branch is overcrowded thanks to careless changes to science tree.

Is anyone even working on that prepatch preview fix to metaplot issue? It's been three months. Could at least integrate rest of the changes into main branch.