Request pre-sales advice: AppleTV4g or AppleTV4k

I currently have an AppleTV3g, iPad Pro 9” and a low-end Vizio HDTV. I have a modest library of iTunes media, and I use the Apple Music service a lot.

The AppleTV3g (as you know) has been abandoned and deprecated by Apple Inc., so now I am planning to buy a newer AppleTV...ah, but which one?

My Vizio TV’s max resolution is 1080p. I am not sure of its max refresh rate. I would rather not upgrade to a newer TV right now. I like to watch HD movies and use Netflix and PBS Passport and other streaming programming.

If possible, I would like to know when Apple Inc. plans to retire the AppleTV4g. If I could get one and a half years of use, I do not think I would complain.

Will the AppleTV4k work well (or at all) with my Vizio TV? Willl it downsample 4K-HDR and its ilk to 1080p at all or well?

If I do not want to play video games, do I need more SSD storage than 32 gigs?

For both the AppleTV4g and AppleTV4k: will the HDMI cable and the input on my TV set that worked with my AppleTV3g still work?

I hope I have asked my questions clearly enough.