Some of my friends insist on watching movies only in 4K, but once I secrectly played a proper 1080p BluRay copy and they would not believe it was 1080p.

Not much to do with the OP other than that it's been a long time since even the "tech-savy" have watched anything on disc. I guess 95% or more live with whatever potato bitrate they get from streaming services.

Depends on screen size and distance. Super obvious at the right combo.