Well i can say this.
I own a late 2013 27" i7 32gb 4GB 780 GPU model and i game not every day but it isn't far from it also

Yes it will run from time to time with full fans depanding on your game ofc.
But my choice was simple i wanted the iMac 27" eventhough i know a desktop pc will be much faster and cheaper. But it can't compete with the design
I do run Windows 10 from bootcamp because OSX "ghosts" like hell. (Mainly i play FPS games)
I have also my MacBook Pro 13" bought in 2016. (You will need à 15" Pro model for "some" normal gaming imo)
I would deff go for an iMac 27"
- much more visual gaming pleasure
- cheaper/easier and doable to upgrade your RAM
- better cooling if fans run for long period
- and there are a few more of above reasons......