You may be overthinking this.
My daughter’s bf is at one of the schools on your list. He rushed and got a bid but ended up dropping shortly after because all the required events and meetings were eating into the time that he need to focus on academics. He has no regrets. All of his friends who rushed have since dropped as well (many for financial reasons).
My daughter also dropped her sorority this year. I just asked her if she had any regrets and she said no.
I agree with others that as long as your son keeps an open mind about other social opportunities, not being Greek won’t have an impact on his college experience.
If he’s athletic, there are many club and rec league sports opportunities also.