The size of the dot you choose should be determined by the type of shooting you intend to do. The problem with all of these is that I don't think you get any magnification. CA compliant models are available in 3.4" and 5" barrel lengths. I think the small reflex red dots are what need to go on the P22. trigger pull for double action and a 4 lb trigger pull for single action. Double/single action trigger has an 11 lb.
WALTHER P22 RED DOT MANUAL
It has a loaded chamber indicator for quick status inspection, an external slide stop locks back on empty and three safeties - manual external, magazine disconnect, automatic firing pin block safety. The PDP has been designed to be more modular than previous handguns, and has been described by Walther as their flagship handgun. The slide has front and rear slide serrations for a non-slip surface with distinctive Walther styling. The Walther PDP (Performance Duty Pistol) is a 9×19mm Parabellum semi-automatic pistol designed in 2021 by Walther Arms as a replacement for the Walther PPQ. Low profile three-dot polymer combat sights won't snag clothing and are rear adjustable for windage. 22LR Pistol, Rare Two-Barrel Set with Interchangable 5' and 3. Trinity Weaver Mounted red dot Sight for Walther p22 qd Tactical Home Defense Optics Accessory Aluminum Black Picatinny Weaver Mount Adapter Class IIIA 635nM Less Than 5mW. The Picatinny rail makes it a snap to mount a light or laser. Standard P22 models have a threaded barrel for easy addition of a suppressor or to change to/from a 5" target barrel. Walther adapted the tactical styling and performance design concepts from their centerfire handguns for the P22 rimfire pistol.