I took both the SAT and the ACT and I believe that my scores for both are competitive. However, as it costs money to send both, I only want to send official reports for one of the tests. If I self report both, am I required to send official reports for both?
Only if the college requires you to send all scores. Otherwise just pick one.
I would send both to your reaches. They cannot use your scores in the ‘stats’ if they are self reported, but can if they are officially sent. Likely that your reach schools are where those numbers are going to help them more, so send them.
Edited to say: I take that back. You have a 36 on the ACT (!) That would have been good information to share on this post. No, I would not send nor even report the SAT. I’m guessing you took the ACT after you had already sat for both SATs - or else why would you bother with the SATs.
I would not give College Board another dime - don’t send the official SATs.