I don’t think I’ve ever seen the words CC and “super laid back” in the same sentence before!
This is not necessary. @lindagaf 's advice is spot on. Have your son try each test at home (I had one SAT kid and one ACT kid so don’t assume that one is better than the other until he tries them out.) If the scores are roughly equivalent, have him prep for the one he prefers. Some targeted prep of any weak areas and a few timed practice tests at home is enough prep for most students.
Very few schools required subject tests anymore, even before COVID hit.
If your son pursues activities he genuinely likes rather than trying to mold and shape himself into something he thinks colleges want, he’ll probably be happier and it sounds like he won’t lack for fine college options. Big hugs to you and best of luck.