My understanding is that Rift S and 5k+ have similar clarity and SDE. The rift S might even be slightly better actually, but it has a tiny FOV and a bad refresh rate.
Imagine the same detail of the rift S with double the FOV and 120 or 144Hz, that’s basically a 5k+. As I said, I’ve read total 50/50 responses. Some people view the 8k+ as an obviously major upgrade, and some actually prefer the 5k+. Unfortunately these aren’t something you can try out in public, not that you could with COVID going on anyway.
To be honest, the 8kX and the artisan are the only things I find interesting from pimax atm. The artisan has even better clarity than a 5k+ with the same refresh options. Yes, a smaller FOV, but max FOV has distortions on the 5k, 8k etc. I play normal FOV on my 5K, 120hz exclusively. Not to say it’s any are bad HMDs, but for the price the artisan is actually quite compelling.