We've had "Prime Video" for a long time now and have had no issues. Our old Internet was 150/5 and with two TV's streaming at the same time, it was smooth sailin'. Last month we moved from Comcast to CenturyLink Gigabit and in doing so lost HBO. So I have just added it on as a "Channel" and it's OK but not as inclusive with extras as the HBONOW app that I use on my AppleTV 4K. But since Gramma's TV in her "office" had the NOW app that disappeared when Samsung upgraded the HBOGO app, we could only add-on HBO to Prime instead of using the NOW app. I'd love to get BritBox, but need to do more looking into it. They are gearing up to compete with Apple TV+.
4K HDR is great, Audio is great all when present. The only complaint I have is all these OTT networks are mixing their International programming and I grab onto a program that look interesting and it's Spanish or French with subtitles. I watch a program to "Watch the Program" not the subtitles. I just wish they'd separate or label them better. Well and another that is there is so much to watch that it gets confusing. Also they are trying to find their "Center" and dumping programming that was a mainstay. Other than that it's a great benefit to having Amazon Prime. I think you'll enjoy it.