I only use FireFox and or Edge. I don't have a VR headset. Was that a requirement to play the game?
VR is not a requirement to play the game, though I made the DriveVR5 prototype for VR, and added non-VR support mainly for quick testing of certain features and to allow for cross-play.
If you get a chance to try out a VR headset some time, I highly recommend it. In this prototype in VR you can even grab onto the virtual steering wheel to control the car, and the sense of speed in VR makes the experience so much better!
Did you also try DriveVR2? (https://vivido-design.itch.io/drivevr2) That seems to run fine in Firefox for me. For you too? In that version you race on tracks, set lap records and can create your own tracks and easily share it with others. You can create the track anywhere within the giant cityscape and it's also possible to press "C" to go into fly camera mode, go anywhere in the city (hold Shift to move faster when in fly camera mode) and press "J" to respawn the car below the camera position. Just make sure not to drop it too far above the floor, or the car will likely fall through the surface. You can freely race through the giant city.
If you like to get chased by cops while driving, you could try ChaseVR (https://vivido-design.itch.io/chasevr). If you play that in VR you could also get out of the car to run around and shoot arrows (including explosive ones) and shoot grappling arrows to fly around the city. Also in VR you can get into the helicopter and fly around and shoot at the cops and drones.