I have shot quite a bit of those powderless .22s.
I have bought every kind I have run across trying to find the quietest.
Be aware that some have a little bit of powder to step up the velocity a bit.
The quietest I have found are the standard Aquila "sans poudre"
The loudest were Remington.
But for the most part I just use CCI CB caps. The shorts shoot as well as the longer ones, so I just use those. My Marline 39 holds 22 round
They caution you not to use them in long-barrel guns, but I have had no problem with them.
The longer the barrel, the quieter they get. From a 24" barrel they are quieter than a springer airgun. You only hear 2 sounds - the firing snap, followed by the impact of the bullet.
Kinda fun chasing tin cans across the back yard from a chair on the deck.
Fired from a small pistol they are almost as loud as a regular .22 from a rifle.
They are fairly accurate. I guess they would group around 1.5 inches at 25 yards, which is about the limit of their range.
Not much energy delivered. Anything more than a headshot on a squirrel is not recommended. They would probably dispatch a skunk at point-blank range. I have never shot any sort of animal with them. IIRC they chrono at around 500 fps, with a 36-gr bullet.