@gsuberland good feedback, thank you! i believe the SoM does not need decoupling on the carrier as it has it's own decoupling at the input. i'll look at the caps in more detail, thanks!
for TVS on those, my thinking is that i'll have TVS on the "port boards" with the actual outside connectors. there could be some static events from handling the internal cables of course. but i wasn't sure if it's a good idea to have TVS on every board's internal connections as well.