I have a Q80 and a 1x. They work just fine together. I use the smart features on the TV and they work fine. I can play games in 4K and they look ridiculous. Non-4K games play nice and smooth on the tv. I also have a Q60, it is only connected to a 1S. Games and 4K content still look great. Obviously no 4K gaming without the 1X, but all games still run smoothly, just not quite as smoothly as the Q80.

I also had a first gen 4K Samsung TV that I always used the smart features on without issue. I replaced it with the Q80 when I decided I wanted a larger screen in the living room. I gave it to a family member who still uses it and its smart features (Mainly Netflix and Prime). Compared to the Q80 and Q60, it is definitely slower, but still useable and still recieves updates from Samsung going on 5 or 6 years.

I'm not saying all Samsungs are created equal, but I assume the higher end ones are kept up to date longer than the lower end ones. I've never dealt with a 6 or 7 Series to know if they're worthwhile but I have a smaller 1080P Samsung smart TV that is going on 4 years that is still quick and simple to use. This is all just my experience, maybe I've been really lucky.