Many games with multiplayer features require Galaxy for those multiplayer features. You can consider this DRM-equivalent if you want. However, every singleplayer game on GOG will work without Galaxy installed, and that singleplayer gameplay will be completely DRM-free in every possible way. (That's at least 99.6% of the games on GOG, but eyeballing the 22 games which don't specify that they're singleplayer games, most of them simply have incomplete metadata, so it's really 99.9% of them.)

Depending on the launcher does not imply DRM. It could be a features-dependency to make the old games working or just allow certain features.

Really? What games are those? I've not encountered a single one :/