Yes, for on-ball screens (and a fair number of off-ball ones), I'm controlling one of my two defenders involved in the action.
I haven't labbed this in a concerted way, primarily because 2K stupidly doesn't allow us defensive controls in Scrimmage mode, but I have a feeling that, in order to have P&R switching work, if you are controlling one of the defenders, you have to make sure you definitively move in accordance with a switch.
For example, if I'm controlling the big, I have a sense that, unless I basically hedge very hard, my small might go around the screen and go back to his man.
P&R Defensive IQ surely plays a roll in how consistently a defender will play his part in the scheme, and even for high-level defenders, mistakes will be made.
Frankly, even if not playing switch, switches will occur. So it still can make sense to construct a lineup that is very flexible in this regard: i.e. big, strong guards and laterally fast bigs.
I really think that a big, fast, strong, and high Def IQ team could do surprisingly well against even a loaded offensive team controlled by an experienced player. Last year, I was running Diamond Oscar, Diamond Kawhi, Amethyst LBJ, Diamond Millsap, and Diamond Draymond as a lineup and they could really throttle down on the other team.