I would echo the suggestion of others that you not bother with a smart TV; just pick one you like and then get a Roku/Apple TV/whatever (I think Linksys may sell one, etc.). Cheaper and it future-proofs you a little more. I can't speak to the Roku but it is possible to "jailbreak" many Apple TV models, which gives you the ability to stream many more kinds of content through that box. Might work for the Roku or others, as well.
We are able to stream to our "dumb" TV by initiating the content on either our iPhone, iPad, or MacBook; recent versions of those can relay the video to the Apple TV which then feeds the TV. No issues with wireless speed; in fact, if the picture breaks up it's far more likely Comcast's fault. Oh, BTW, "recent" in the case of my MBP is 6+ years, so anything recent ought to be able to do it. So if it is content we cannot get through the Apple TV itself, we can get it through one of the other Apple devices. Works well for what little we watch.