Do I need cat4 sunglasses or glacier glasses?

Hi all!

In the early stages of my mountaineering journey here and looking to get a solid pair of sunglasses (who knows, maybe ones I can use cycling as well). I wear glasses and unfortunately can't stand contacts so buying prescription cat4 glasses just for my alpine endeavors is a little pricey. For the foreseeable future, these endeavors would be in the Alps and Norway.

• Are cat4 glasses are needed in the Alps in your opinion?
• How are your feelings about the side covers? Are they needed? I heard fogging is an issue.

thanks for all your inputs!