I usually refer to the bellow diagram with regards to occlusion effect and earmuffs;
View attachment 46665
The bigger the cup is around the ear, the less occlusion effect you experience, so I'd say you're pretty safe with earmuffs, although you may be able to hear a slight amplification of the sound. Here you also see that the deeper ear plugs are inserted, the less occlusion effect you experience.
Regarding hitting the ear muffs in walls or such, I wouldn't worry that much about it. I have pretty bad sound sensitivity and spikes very easily, but such brief sounds rarely cause any issues. I would try to avoid it though, because it can be loud. But it has happened many times to me without consequences.
All the best,
Stacken