The Pimax Vision 8K X is the highest-end headset that Pimax offers and is best suited for extreme VR fans with an excessive budget. You’ll need an RTX 3080 or better to drive the HMD to its best potential. You should also expect to spend much time fine-tuning the settings to dial the headset in for each game for the best performance. If those things don't dissuade you, no other headset compares to the Vision 8K X.
The PIMAX 4K VR is a neat little headset that has a higher resolution screen than the HTC Vive or Oculus rift. But what it makes up for in terms of visual acuity it looses in terms of the lack of motion/touch controllers - which makes playing VR-only games impossible. That said, games which do not require touch controllers and VR media work flawlessly and better than the Rift or the Vive. So if VR media is your primary concern then the PIMAX will actually serve you better than either of the two giants. It even fares pretty damn well in games like Elite: Dangerous which do not require touch controllers but support VR.
The Pimax 5K Plus is not for everyone. The headset is expensive and demands a lot of tinkering and tweaking to get the settings perfect. If you’re new to VR, don’t get a 5K Plus. But if you’re a VR veteran and want something new and unique, peripheral vision in VR is a experience that will rekindle your love for VR.