Have you looked at wiki to read up on the "standards"? My older, ("n") but not antique, modem/router courtesy of BT delivers 30mbps to a newish tablet the other side of the house, from circa 39mbps as it comes in to the house. (About half what I am apparently paying for ). What does your modem/router suggest you should be getting?
But mine coughs and splutters to keep an older Sony tv in full stream, so I'm guessing that is the tv's receiver's problem, not the modem/router.
So many complex things in today's life. The whole marketting thing of "New" should be banned. You get one "new" service, and it turns out that nothing else fits it....
A friend says that we can blame all this marketing "new" stuff on Dulux who got heavily in to "new" back in the 50s.