|It's easier to stick to the same vendor, but you can work around mixing devices.|
You only need the one unit connected to your router, you can then run 3 more quite easily in different parts of the house - I have the same set up here, only using 2 at the moment but they could easily handle more (mine are 'Devolo' branded & I can recommend them). Just plug & play essentially unless you need to add extra security which they all offer (in case you share your mains with another house or whatever).
The ones with extra ports are, as you say, just switches which are added to the network adapter. These devices really are the best thing since sliced bread as far as home networking is concerned.
"I've always been mad, I know I've been mad, like the most of us..." Pink Floyd