>>310492587
Pavlov is the most populated VRFPS, Contractors and Onward are the next closest.
I think Pavlov has a free beta for the Quest port you can mess around with if you set up Sidequest, but it's pretty limited.
Assetto Corsa is probably your best bet for multiplayer sim racing right now. rFactor 2 is supposedly good too, but I haven't tried it yet. iRacing also works in VR if you want to throw a bunch of money at that.
Any good USB C cable should work now, but you're probably better off looking for a list of stuff that's confirmed to work.
If you mean Dirt Rally 2 it looks fine on my Index, so it sounds like you've got an issue with the way Link is set up or something.
>>310492740
It's a lot harder to mod on Quest, and some mods don't work at all. Also the new version that mods don't work on yet is the only version that runs on Quest 2 right now.