Im saying "legally" doesn't matter to anyone other than lawyers and judges who don't understand the concept of consent.

Steam is not the same since you dont truely own the games you buy.

Your sentence make 0 sense, you don't truly own the game you buy on ANY platform

I should have been more precise:

From the legal perspective, you don't truly own the game on any of the platforms.

From the technical perspective, the moment the game is on my PC I can run it.

For passing games to your heir legally, there is no way.

For passing games illegally both steam and gog work. For steam, you can download the steamdll and backup all your library and be good to go. For gog you don't have to do that, but if we are talking of illegally backing up all your games for after you die, you are good. As long as you are alive, you can play both gog and steam games for as long as you want.

Interestingly, you can illegally share games with your family in both platforms when you are alive, but you CANNOT legally share your gog games with your family, only Steam ones.