BoyWatchIt: I am using a Mac M1 and I'll go back and take a look at the icon you are referring to
Unfortunately, Macs are terrible for gaming, and very few games are available for them, and most of the good games are not available for them.
Yes, you could say that GOG is not Apple friendly, but that's not just a GOG-specific problem; that is an industry-wide problem for
all computer game stores, since the people who make the games are not Apple friendly and they generally do not bother to design their games to be compatible with Apple/Mac machines.
Therefore, if you are serious about wanting to play games on your computer, then you are going to have buy a personal computer, one which is not an Apple/Mac.
As for do you need a controller: if you want to have a comfortable and enjoyable experience while playing modern computer games, then yes you do, since most modern games were made for consoles - which
only use a controller, and therefore modern games are usually
designed specifically for controllers - and then they become ported to computers after that.
The best controller to buy is probably an Xbox controller (they work with both Xbox consoles and also computers too), since they are specifically designed to work with Windows-based computers, and since Xbox controllers have the widest range of compatibility with most games.