Homeplug adapters are all compatible with each other, even across manufacturers. You can expand as you wish.
With one you feed in the LAN signal, and with all the others you can tap it off. It's like a huge LAN switch that takes up the whole power grid :-).
You shouldn't use them in power strips, because then the signal will be bad.
And you should run them on the same circuit. If there is a fuse box in between, the signal is very poor or no longer available.