I've been wondering the same, I don't really use a controller very often and currently just have a wired 360 one, but I'd be tempted to invest if it makes a real difference to the experience. Though I guess the PS5 controller won't be as easily compatible with other games.
Should be. Steam has Dualshock compatibility. Though I went with the Xbox Elite 2 Controller since you can adjust the triggers, short, medium or long presses. Stick curve adjustments, stick tension and setting up your own profiles for whatever game. As well as configuring all 4 rumble motors.