Touchscreens are like "secret handshakes":

When driving I may need to fine-tune a setting in a range, OR seek a specific touch- or switch-point amongst a field of identically sized levers or buttons.

My solution is to seek an anchor point with my hand while other fingers do the work. I like hanging my hand on physical knob controls, e.g. for volume, in a non-input direction and without motivating force to change the underlying value.

The problem with anchoring is that my arms jiggle like bouncy bridges, when driving over any kind of bump. This external force disrupts my solution. It can be somewhat solved by tighter grip on the knob or non-input region of the control.

Additional problems come from having touch-screens - they create an extra physical problem of reducing the anchor-safe areas on the dashboard.

And, I workaround touch-screen's problem of "need to anchor" vs "can't touch without committing to change" by tenting my hand on dead-zones of the screen, or around the bezel or surrounding non-input surface.

So touchscreens, for me, add complexity to using the vehicle as a tool to accomplish the deed. Like "secret handshakes" are to greeting.