Yes, it is possible.
Yes, it is possible.
Yes, you can set up a setup like that. Connect the TPLINK adapter via powerline to your network switch, which includes extra Ethernet ports. Then plug your devices onto the switch and the other end of the adapter. This configuration works well for routing traffic through the router while using the TPLINK adapter as an Ethernet source.
If you haven't purchased the power line adapters yet, I'd look into alternative solutions, as power line connections can be inconsistent—works well for some users but not for others.