anothername: Does doubleclicking the W3 on the desktop not start the game directly? The clients are nice to keep patches and occasional refresh the installer archive but everything else; even just starting a game... eww :/
edit:
Most games I know have an ingame button for screenshot but should I jump between many games and do printscreens often in all of them I'd be on the lookout for a program/tool which does that too.
But usually... I just doubleclick and play; and then mostly one game for an extended period.
I don't launch games via gaming clients because the games don't work without the gaming clients, I launch games with gaming clients because I purposefully explicitly want to use a gaming client to launch my games and have gaming client features available that I wish to use.
All GOG games install, launch and run perfectly without the optional Galaxy client. I don't even need to test it because nobody is required to use Galaxy, and every game is downloadable without Galaxy and should work fine as advertised. As such, of course Witcher 3 will work if you run it from a shortcut on the desktop or start menu, but that doesn't give me the experience I am looking for personally.
Sadly, it has been my personal experience that most games do not have a screenshot function built in as a growing trend over recent years, so one is left having to resort to using the Windows printscrn key and hope that that works, and have to ALT-TAB out and paste the screenshot into Paint and save it and hope ALT-TAB did not hose and crash the game, or you have to use Steam client or some other 3rd party software to do screenshots. To the best of my knowledge and research as of about 12-14 months or so ago The Witcher 3 did not have any built in screenshot function that I could ever find anyway, nor do most other modern games I test out. I think the developers leave it out because they design for Steam and just leave it up to the gaming client to handle or some other 3rd party overlay management software.
Most _older_ games that predate gaming clients or were in the early years of gaming clients have screenshot capability built in though.
I think that one would be hard pressed to find a game that has built in video broadcasting to your friends and family built into it though, and that's something that I do like to use from time to time. There are 3rd party programs that can do that as well, but I already own one - it is called Steam and I already have it installed, so I just use it rather than have to use yet another 3rd party program that needs yet another online account. :)