What do you guys use for 4K screenshots on the PS4 Pro - PNG or JPG? Is there much of a difference?
Always PNG. And, yes, there is a big difference. PNGs are uncompressed, JPGs are compressed and the overall image quality is impacted.
How are you taking screens without the HUD visible?
I just realized that I didn't reply to your PN sooner. I'm sorry.
The screens that you quoted (with the Injustice logo) are taken in the randomely playing matches, that start when you are in the game start menu and don't press any button for a while.
The other screens (without any logo) are taken in training mode. There you can completely disable the HUD.