Why does adding a post-process improve the render framerates on Mac retina screen?

[sebavan]

@xiasun let s keep only one thread open please as I can see the question being discussed there:

Engine's antialias option has no effect

This is not the case. In the 3rd case you have a separate pass that relies on depth test. To compare apple to apple you should enable it in the canvas options for case 1 and 2 so overdraw could also happen.

and a bit there Possible performance bottleneck on high resolution devices (MacOS) - #17 by Deltakosh

Can you try to turn depth test on in your first PG ?