I did a "quick" test. 1080P MP4 file with screen screen. Project length was 16 seconds. The green screen effect I used was Studio Chroma Keyer. I masked one of the people on the side as you can see in the image.
On my computer, exporting the same as the timeline, it took 1:53 to export completely. I had Task Manager open, and the max CPU usage was 17% and max GPU usage was almost 5%.
IF there was a project that had much longer clips to mask, it's going to take some time to export.
Is this slow? I haven't compared this to other editors export speeds, so can't say. Does the software utilize my hardware? Not in the least.