Wrestling is much safer from a CTE perspective. Concussions can happen, but aren't that common.
The weight cut is less dangerous at higher bodyweight, so as long as he isn't trying to lose too much in the 24, 48 hrs before a match he should be OK.
The biggest risk is that Wrestling is a good physical base for MMA. So he may end up getting punched in the face anyway. 🤷🏿♂️