I haven't tried any glass protectors.
I have these plastic film protectors paired with this matte black case:
https://smile.amazon.com/gp/product/B0BHZSGTW8
the case keeps you from seeing the edges of the protector and it feels just like glass.
I got a scuff on my first protector. I don't know if the same hit would have marred the watch but I'm happy not to have found out. I replaced it (it's a pack of six) and the second one is in perfect shape a month later.
Ringke Slim [Anti-Yellowing... https://www.amazon.com/dp/B0BHZSGTW8?ref=ppx_pop_mob_ap_share
It's practically imperceptable. I noticed the glue a bit at first but was able to easily peel away the excess glue. I haven't needed to remove the screen protector yet so I can't answer how easy it is to remove. In case you're considering using a case, I had the Ringke Slim case and while it fits over the screen protector, I could no longer turn crown dial. The Spigen Liquid Air case still fits with the screen protector on.