Comet support achievements and are already usable with Heroic if you launch it yourself.

Cloud saves are already supported by Heroic ; Comet can already be used if you launch it yourself but will be integrated in the package in the future. Comet support online features and achievements. Heroic + Comet = Gog Galaxy

I use Heroic for installation, updates and cloud saves, and Comet for online and achievements functionnalities, no need for Galaxy via wine anymore.