To varying degrees.

Throttle cables have been replaced with wires for at least 20 years. Rack and pinion is slowly going away but odds are still pretty good that an arbitrarily chosen new car won’t use steer by wire; that’s still pretty niche. Shift / clutch has been electric for a while now on most cars but there’s still some “pure mechanical” shifting cars out there.

An all digital break system is probably going to take a _while_ to become standard.

Four wheel steer was a common use case for steer by wire in the past.

Throttle-by-wire, yes: any modern car has this. Steer-by-wire or brake-by-wire, no. If the power dies, you can still steer to the side of the road and apply the brakes.

The Cybertruck is steer by wire.

Infinite had it with a backup, but it was bad.

On the good old BMWs with hydraulic steering, you could get Active Steering, i.e. variable steering. They basically introduced a planetary gear set: https://www.youtube.com/watch?v=unL8HpMeVTA

If today you buy a BMW with Active Steering it means you get rear-wheel steering (on top of the standard front-wheel steering, but don't tell the execs, you don't want to need a subscription for front-wheel steering).

On BMWs since the F* (with the electric assist steering) variability was achieved by a variable-ratio steering rack.