Well I don't think Civ 6 was ever in danger of not coming to the mac but it's nice to see Sleeping Dogs, Deus Ex and Mad Max. Let's just hope it's a good port that's worth the money.
Well, all I can say is that it is running beautifully @2560x1440 on my 27" late 2015 iMac 4.0GHz i7 395X 4Gb.
Haven't looked to see if there're is a built in benchmark, but I'll look later.
There doesn't appear to be any built-in benchmark, but just using the Steam FPS counter performance is quite good!
I'm running a 2013 27" iMac (i7 3.5, 16GB, 780M GTX 4GB) and get a locked 30fps with vsync enabled on the recommended "high" settings preset.
I could probably tweak it a bit and increase fps, but I'm liking the eyecandy.