Kein;
Actually, there were a couple complaints about achievements. In particular there was an achievement for finding a certain NPC, but it was triggered just before you got close enough to trigger the cutscene, so the name of the achievement was a bit of a spoiler.
Lotrotk;
There is more profit for developers with direct sales. See the blog post
Of Kickstarter & one thing I think game journalists should do. I don't know if the game itself would be any different between GOG and the Larian Vault.