I've used this one on both my 3 and 4 and never had issues. I live in the Midwest where it can get pretty humid.

(3Sets) DIACUBE Full Cover... https://www.amazon.com/dp/B09FKD5524?ref=ppx_pop_mob_ap_share

I only use matte/anti glare screen protectors which aren't everyone's cup of tea.

It's not clear. it makes you able to see your screen in the sunlight without turning the brightness up all the way. It helps if your eyes are sensitive to the brightness of screens. It's also anti fingerprints.

This is the one I bought (3Sets) DIACUBE Full Cover... https://www.amazon.com/dp/B09FKD5524?ref=ppx_pop_mob_ap_share

It's says z flip 3 but I also used it on my 4.