I would wager M+ level due to a couple of things (also with the context I only know USPSA classification and this was a Brazilian video).
1. He had the mental bandwidth to execute with confidence fully within his skill set.
2. He had excellent recoil control and transitions
3. He didn’t miss. He took enough time, but not too much.
4. He was very comfortable with shooting on the move, nice low and aggressive.
The hallmark of M/GM is confidence without delay and knowing how fast but not too fast to go.
That’s a very different level than B and even most A level where there’s often fairly gross misjudgment about how fast is too fast.
Here you could tell that the good guy knew how fast the fast shots needed and how slow the slow shots needed.
@Clusterfrack what say you?