It is not a Crystal, but similar. I am owning a Pico 4, a Pimax 5k+ and currently I am testing a 8kx - I can run rF2 at high details with the Pico (I am not using to much oversampling and scaling in SteamVR, around / near 100%), which does also work with the 5k+ - difference between 5k+ and Pico 4 is their resolution and FOV.
The FOV on the 5 and 8 is incredible.
Also I like the sound of the DMAS and with the 8kx there is 5.1 sound which is quiet good compared to Pico or 5.1 headset ... with the Pimax 5k+ gauges and e.g. speedometer can be read but you 'll notice the lower resolution - with 8kx detail level is impressive.
The 8kx is running at round 75 FPS with large FOV enabled and I am using quiet the same settings on SteamVR (I have not switched to PimaxXR for various reasons until now) but it is driven by a 3080 and the GPU is sweating ...
Both (5 and 8 one) are not upscaling - I am using native resolution.
The FOV is the game changer - with the Pico you always feel a bit like skooba diver, which is not the case with the Pimax sets.
The Pico is easy to install .. as an Oculus Rift S e.g. I was using before the Pico and the Pimax.
The Pimax is somewhat harder to install and configure - tracking does take some seconds until it is working when I start playing so I think I need to place the base stations a little bit different (I am thinking of using base stations 2.0 in order to use four ones). IPD settings is tricky ... and with the 8kx I am still not satisfied (so I am thinking of returning it). At least IPD offset (software feature) is pretty hard to adjust and most people say colors need adjustment, too (there are some videos of MRTV around).
I have found the 8kx used in a pretty good shape, but I would not have spend 1300 to 1400 Euros for it to be honest.
edit:
I have read a lot of tests and user reviews about Pimax and I would like to say that I have good experience with their support concerning new lenses for the 5k+ (one of them was a little bit blurred after two years), but the 5k+ (which is around 4 years old) seems to die slowly (I have white pixels flashing around the display, one pixel is dead on the left one (looks like a crack in your windscreen ;-) ) and sometimes there is kind of ghosting on the left display as well as it crashed two or three times and became unresponsive)
So this makes me think even more returning or purchasing the 8kx ...