Itz is pointless to debate about native and SS resolution and even compare Vive, Rift, and Oddisssay with Pimax8K. Vive, Rift, and Oddissay have approximate same FOV of 110° and Pimax8K or 5K got 200° FOV.
So there are multiple factors which determine the quality and after all impression in VR usage. 3 major factors which effecting on itch other and creating final VR impression are the Native display resolution, PPI what we could call display hardware resolution and effect on SSD directly, and PPD what we could call end resolution what represent what you can see in the final in VR usage.
There is the 4th factor which also affecting on end VR impression make difference only between Vive/Rift/Oddissay vs Pimax 8K/5K and that is lenses, not just because of 110° vs 200° FOV it is also affecting on PPI and PPD because of the different magnification factor.
This 4th factor take it with little grain of salt because it is based on some assumption and maybe not fully correct and that how much really is different and if it is at all we will see only after first serious comparison after lifting NDA.
To not now repeat all this year's discussion about displays resolutions, PPI, and PPD I will just for example post the famous VRMAN66 YT video with a comparison of the 3 different displays like we have today and are used in 5K and 8K Pimax.
Deepoon E3 is using the same PPI as 5K and 4K same as 8K so that is like difference should look like between 5K vs 8K. To get the picture.
this is all comparing under same lenses magnification under 110° FOV VR. Similar results you will get comparing newer WMR's or Vive PRO.
Now I'm coming to that 4th factor, the lens magnification. More ao less all 110° FOV VR have a similar physical size of the displays and use similar magnification on lenses. So this is not changing factor if you are comparing only 110° FOV VR's but 5K and 8K are 200° FOV VR's. Let's compare it in numbers:
Vive/Rift - 100° per eye / 1080 pixel wide per eye = 10.8 PPD, PPI = 430
DeepoonE3- 100° per eye / 1080 pixel wide per eye = 10.8 PPD, PPI = 520
Pimax4K - 100° per eye / 1280 pixel wide per eye = 12.8 PPD, PPI = 800
Pimax5K - 150° per eye / 2056 pixel wide per eye = 13.7 PPD, PPI = 520
Pimax8K - 150° per eye / 2056 pixel wide per eye = 13.7 PPD, PPI = 800
WMR/Vive PRO - 100° per eye / 1440 pixel wide per eye = 14.4 PPD, PPI = 520
Pimax5KX- 150° per eye / 2560 pixel wide per eye = 17.1 PPD, PPI = 800
So compare this pictures and check the differences in numbers so you can imagine how much better could be a picture before real comparison after NDA lift.
But where is here magnification or 4th factor you are talking about? Yea, we are not finished yet. As you can see major differences are not just PPD but PPI and most of all FOV. This is maybe is not an exact value but we will use it to get the point. To immerse inside VR we need lenses to magnify picture and stretch it to this 110° so it magnifies it, let's say 3x. to get a picture about SDE and put value for it in numbers will be if we divide display PPI with Lens magnification factor. So let's do some SDE comparison in numbers using this values and you will see how this video confirming this numbers.
Vive/Rift - 110° FOV, PPD = 10.8, PPI = 430 / 3x magnification = 143 SDE
DeepoonE3 - 110° FOV, PPD = 10.8, PPI = 520 / 3x magnification = 173 SDE
Pimax4K - 110° FOV, PPD = 12.8, PPI = 800 / 3x magnification = 266 SDE
Pimax5K - 200° FOV, PPD = 13.7, PPI = 520 / 2,2x magnification = 236 SDE
Pimax8K - 200° FOV, PPD = 13.7, PPI = 800 / 2,2x magnification = 363 SDE
WMR/Vive PRO - 110° FOV, PPD = 14.4, PPI = 520 / 3x magnification = 173 SDE
Pimax8KX - 200° FOV, PPD = 17.1, PPI = 800 / 2.2x magnification = 363 SDE
You can notice that on 200° FOV VR's have a lower magnification factor than 110° FOV VR's. that is to keep proper aspect ratio in 150° FOV per eye because of display ratio and FOV ve need different magnification. Less magnification means less SDE and increasing size of VR pixels what will result in additional increases of the picture quality.
All these pixels calculations, SS, and other stuff are pointless because VR is based on individual impressions based on multiple factors combined in general picture not just on individual technical parameters. SS is used in certain titles to increase more sharp picture and details needed to play such title but needs for SS is depended from title to title not related to VR hardware its self.
Now you can see what is my prediction based on well known pieces of information and assumptions we got right now and I won't debate about it because no one can confirm it right now and will be interesting to see first serious reviews which will tell us am I right or not.