I know many people who use these home plugs and they work very well. If you opt for plugs with ethernet connections then there should not be any discernible difference in speed that you get from connecting directly to the router. Wifi connections usually are slower even when they are from the main router so you will more than likely have a reduced speed if you opt for these. Try and get home plugs with mains through sockets so you still have a power point available to use after you have plugged them in. Remember that they are portable too so you can physically move them around to different points in the house.
I have not used these myself so cannot personally recommend a specific brand but no doubt you will get some recommendations from other posters.