All the time I have people come in to work wearing a mask, which is fine normally, good for them, but they are wearing them on their chin, chin diaper style. Not covering up anything. Or at best just their mouth, sometimes. Nobody is making these people wear a mask anymore, so why are they doing it at all if they are just going to do it wrong? Is it an attempt at a political statement? A lack of education? I end up baffled for a while every time I see one of these people.
A mask does make it harder to breath. I have ashma and I can only use certain masks and they have to be pretty fresh. Absolutely they make glasses fog especially so if you do not have certain coatings. Well and a good mask which is hard to find. For me some 3M masks fit well enough and are also designed so they do not seem to cause fogging as much. As far as understanding. Some people are very visual and less auditory. My wife is. So yes some people understand language better seeing the face. Say nothing about lip readers.
This is all true from my experience to some extent though it feels overblown at times and may well be. None of this prevents me from using a mask when needed for example.