The Cosmic Avenger
Thinks s/he gets paid by the post
If your reason for 'cutting the cable' is to save money then I would purchase any needed router/modem rather then lease it, they aren't that difficult to setup, fairly reliable, and will probably payoff in less than a year. I have an LG OLED TV and prefer using it's smart TV interface with Amazon Prime rather than the Fire Stick but it can vary by TV.
Very much so. Roku is probably fine for most people, but there are some smart TVs whose interfaces are good enough that you might not need one. We have 3 Rokus, but we don't use one of them because the Samsung TV we bought about a year ago has all the apps we use and the interface is as good or better than the Roku, so we use that instead in that room. I also have content in two apps that are less common, Vudu and Plex, and so any streaming device that doesn't have those apps is a dealbreaker for me.