Hi @VR-TECH i use my 5k+ for sim racing (the main reason I got a pimax hmd) and can give you a good heads up from my own personal experience trying and using it on many of the main sims.
I would recommend racing sims in terms of VR quality with a pimax HMD in this order:
AC (original Assetto Corsa)
ACC (needs powerful GPU & VRToolkit otherwise it looks quite blurry)
Each sim requires a couple of tweaks to get working at its optimum but AC & ACC work out of the box without PP enabled as does iracing if i remember correctly and RF2 does too if you use the json tweak to enable support for HMD’s with none parallel displays (this is documented on RF2 website and in their forums as well as on here).
For most racing sims I would recommend using a sharpening filter (see link below) which is easy to use and configurable all from within SteamVR as an app. For me personally I find the clarity and lack of aliasing in RF2 to be the current pinnacle in VR fidelity/realism & the graphics on official premium content are top notch (old content and/or mod content can vary wildly and very old mods look quite terrible). AC is very good too but requires the shader patch and sol mods to bring its graphics up to date, otherwise it looks dated.
The VR toolkit sharpening filter can be found here, along with instructions on how to use it: https://vrtoolkit.retrolux.de/
In terms of whats a better sim, its personal pref but IMO id say the following is a good rule of thumb:
RF2 for multiplayer organised league racing & arguably the best FFB and overall handling model
iracing for the best anytime/random multiplayer action
AC for singleplayer & scenario based AI races or “track day” style events
ACC if you love GT3 and it also has good anytime/random multiplayer userbase, although not in the same league as iracing.
PC2 for singleplayer scenario based AI races, particularly in rainy conditions.