Just get a Shield TV; it supports 4K60 HDR streaming - and no, there is virtually no latency when you stream via Ethernet. It depends on your router/ network NOT your Internet speed. I've even checked with my PC and TV running the same game side by side, and there was no noticeable latency there with Ethernet.
What's more, you'll have one of the best media streamers/ emulator players in your living room as well. The controller the 2017 version comes with is pretty nice as well.