The watch charger is not built in. You will have to use your watch charging cable and route through the watch holder.
For samsung watch - you can turn the adaptor and it will fit samsung watch
i bought this for my 2 offices that i work at to rid of the many wires on my desk. i like the design and the idea of everything in one place. Setting up the watch charger i have to say was a a bit challenging trying to take the bottom cover off to feed the wire. the airpods pro and watch charged quickly no problem but the iphone 15 stayed at 80% for over an hour and thats with the case taken off. a bit disappointed.
It’s depends on the thickness of the case (or, in Apple’s case, they might have a built-in MagSafe component to improve wireless charging). If the phone case allows Qi standard wireless charging, it will advertise that on the packaging.
I charge my iPhone (with silicone Apple Case) every night with a wireless charger (different brand).