A 23 in the front will probably match the
PR-2 for aerodynamics
reasonably well, as that wheel is 23mm wide (ext) and most tubeless 23s will mount to 24 or 25 wide on that width wheel.
My wheels are 18.5mm internal (25mm external,) and the two different 23s I've tried have both mounted to spot-on 25mm wide.
I've noticed absolutely no difference in road feel going down in size on the front tire, but I also absolutely did not pick up some 23s to chase marginal gains-- 23s are a dying breed, and can often be had on clearance on the cheap.
I picked up a Maxxis Padrone and an IRC Roadlite for a
combined $33.