The best description and way to see it work without having one is that video. I can't really explain how it works, besides it "does". One moves the deadlatch, the other moves the bolt.
18 AWG is usually fine for the majority of strike installs for 12V. Securitron recommends larger because of the inrush current and voltage drop for the motor, also trying to make sure there's enough amperage to maintain the torque, like a VonDuprin strike.
In the case of the Unlatch, you'll only need 3 conductors, and if space is tight, you could run individual conductors rather than a single jacketed cable.
They will not work with a deadbolt because there's nothing to push back or a deadlatch. Only way you'd be able to work with a deadbolt would be to use a strike that has a cutout for the bolt throw.
Also, don't forget, you can find an appropriately sized wall wart and use that to power the strikes and not use a supply at all, assuming you're going fail secure. Worst case scenario, you'd need to use keys for a power outage.