I use an iPhone 6s that has 327 PPI compared to 577 PPI of your Galaxy S7 and even if I see the pixels (more clearly than you ) I'm not having an issue at all. The correct optical adjustments are far more important than PPI. The Bebop 2 FPV stream will be 720p if you choose 720p recording also and it's quite decent !
I used analog FPV in the past 5.8GHz and it doesn't even come close to the quality of the Bebop 2 except the latency ... (Analog FPV is close to realtime - good for racing and BAD for your eyes and brain).
I am using the Galaxy S7 Edge, and have no real issues, remember the camera is not 4K, and I doubt the signal being transmitted to the phone is at full resolution. If the full resolution is being sent to the phone you would loose out on signal strength, I believe this is why DJI has a different video transmission system on their better drones to save resources for the control system.
Which mobile phone will give me the best quality of view when using Cockpitglasses FPV?
I used Galaxy S7 but view was not so sharp with pixels visible.
Should we wait for some 4K screens?
I think this is more signal issue,good wifi signal without interferance should give you a good fpv video,....making sure that phone doesnt have to many unnecessary apps running in background might help too