Of course, the speed is a little on the existing power grid depends on how well it is shielded, how far is the way, whether it is an apartment building where the electricity meter hanging etc. I reach in our family house almost the target in 1200, so good values. The Adaptervariente with by gereichten outlet is in my view, the only sensible, in some cases, but I would resort to the adapter with three gigabit ports, then you may save possibly a switch.
So the question for me was exciting but that goes well with the existing devolo? Can I hang the TP-Link's in an existing network?
That's fine!
Both Devolo as well as TP-Link offers a free software with which you can the D-Lan network manage. I have the Devolo in use and could the new TP links easily using the printed security code Add. Only the information about the adapter and the configuration options are limited (which is clearly yes). If it does not work right away, simply dissolve the network again and re-add the adapter (starting with the devolo). Conversely, does it with the TP-Link software probably that I have not tried.
Conclusion: Gigabit network is functioning and that too with other brands. What more do you want?