Steam's DRM may be trivial to circumvent technically but the legal situation is clear: you do not own what you buy on Steam, you cannot resell it, cannot gift it to your friends once you are done, you cannot leave it to your heirs. And no, you don't have any guarantees that you yourself still have access to it tomorrow.

Technically Steam itself dont enforce any DRM on any games. Period.

Unfortunately legal situation is not that different on any platform. GOG gives you offline installers and avoid technical DRM measures in all games, but that's about it - all other things you listed are still missing.