That's just an assumption for worst case scenario in the living room. I'm having a jack installed directly underneath, but I'm seeing a trend in some TVs to ONLY be wifi.
All our current TVs are TCL (Roku) and they do not have ethernet ports (stupid design choice). I'm buying a new one for the living room anyways, but have to account for scenario in which it may not have a port. Plus this current one will be going into the bedroom once I get a new living room TV, so I'll have that situation regardless.
I was also advised that I really should a tri-band router or mesh system. How necessary is that if the node will be hard wired? Can I get away with dual band? Tri's are usually more expensive by a lot.
Gotcha. So in those situations, I would just place an access point in those rooms. They'll feed other areas, but then your primary issue is eliminated.
Of course they will advise you to get that--they're making money off of you.
Your wireless is only as good as the wireless capability
of the wireless client. If you don't have anything that can connect and use triband then it's a waste. And to be honest, with only 150Mbs, it's almost definitely a waste.
I can hit a couple of hundred megabits with my TL-Link Archer c5, my wife's c8, and older Asus rt-n66r, a Netgear R7000, a Netgear R6700--all 'end of life' dual band routers. These are results with a 600/15 and 500/50 connection at two different sites. As long as you don't have any airwave congestion, I don't see you having any problems hitting 150Mbps with even something as cheap as the tplink archer c7 (the better brother of the c5 like I have). In fact, it seems that at least locally, the c7 is in stock for $70 at most staples stores, so I'd just go and pick up 2-3 of these as they will be all you need, and you probably will end up not even using the 3rd one (depending on the layout).