The good news is that connecting it to any PC (Mac or Windows) is pretty straightforward using guides like this. On my PC, it even recognizes the audio channel as a bluetooth speaker, so I think I could get PC audio out through the controller.
The bad news is that most games on Steam support XInput controls (used by 360 controllers) and not DirectInput (used by the PS4 controller). On the Mac, it may not be usable at all; on the PC, there's a tool for emulating an XInput device using a PS4 controller that works okay, though you'll want to test it on a game by game basis, since games that actually support the PS4 controller (Transistor and Broforce so far in my testing) will then register two controllers from one set of inputs.
On OSX, you'll probably need to connect the controller via Bluetooth, then use software like Joystick Mapper to map buttons to the keyboard. A pain, but it will work.
Do you think I'd be better off getting a 360 controller then? I'm trying to make this as easy as possible. I'd need the PC adapter, right? After that would the gamepad automatically configure with Steam on Mac? Thanks.