It depends, running less than 90 fps is borderline and anything under 60 is a vomit comet. Most people have some issues with motion sickness at first but after a few days your brain adapts to it (so called “VR legs”). I regularly play games with lots of fast locomotion for 4+ hours at a time and have no nausea at all. Subnautica with an xbox controller in particular would send most people to the toilet after 60 seconds, which is a shame because it’s the most profound VR experience I’ve had.

Depends. I get horrible carsickness just riding a bus or a plane, so I get some motion sickness in VR no matter how high of FPS it is, no matter how low the latency. I sometimes get motion sickness playing games on my monitor too though, so I'm definitely in the most susceptible category for this stuff.

Like other said though, the worst of it goes away after using it a few times. I noticed though that if you're really susceptible to motion sickness, you basically need to adjust to every type of locomotion or movement individually -- and any vehicles or cockpits are still totally unviable for me still, from No Mans Sky to American Truck Simulator.

Though it's not just one kind of locomotion either -- I adjusted to head-position-relative smooth locomotion with a joystick on a flat surface at a walking pace, but what about downhill at a running pace, on horseback? Then I have to spend another week getting used to THAT. Or what about smooth locomotion circle strafing in a dungeon around a bunch of skeletons? Another week. And I still can't handle any camera rotation at all.

Not really. Keep in mind that getting the headset out in your room is very different to getting a whirlwind tour in a shop. You can just sit down and gasp at the sensation of seeing the trigger move in sync with IRL

Like others have said, it really depends on the game for me. I have the Oculus Quest 2 and some games (Beat Saber, Half Life: Alyx) are fine, but some like Star Wars Squadrons make me really nauseous.

Depends on person, the game mechanics and the hardware. Oculus Quest 2 is very nice HW for its price. Shame you are locked in with a mandatory FB account.

It's entirely down to whether the experience retains 1 to 1 movement between your head and the camera in the game or whether joystick movement or in-game animation yanks control of the positioning of your head/camera and moves it somewhere your real/physical head is not.