I have used Steam on Linux for some time, of course many games are Win only but the choice on Linux is not bad, I guess the situation has improved thanks to the introduction of SteamOS.
In addition, often you can play Win games using Wine, while on a Mac [EDIT: the following is true only if the game needs Vulkan or OpenGL > 4.1] the only way would be using bootcamp (which means you have to reboot every time you want to play).
Disclaimer: I haven't used Mac OS in recent times so I may be unaware of other solutions.
You can use Wine perfectly well on Mac, as far as I'm aware. I have used PlayOnMac (a wrapper of Wine) for Artemis Bridge Simulator and it works great. Though Wine is used more often on Linux, I think, so it may be more stable.
You can, but it's limited because of stagnation of MacOS graphics stack. While Wine on Linux continues chiseling at DX11 support, it's not going to happen on MacOS (no OpenGL beyond 4.1). Same goes for Vulkan. Games like Doom (2016) can work in Wine on Linux, but on MacOS - no dice.
You are right, I should have worded my comment differently, Wine can be used on Mac OS although it will not run some recent titles due to the issues mentioned by the user shmerl in this thread.
In addition, often you can play Win games using Wine, while on a Mac [EDIT: the following is true only if the game needs Vulkan or OpenGL > 4.1] the only way would be using bootcamp (which means you have to reboot every time you want to play).
Disclaimer: I haven't used Mac OS in recent times so I may be unaware of other solutions.