When to send all SAT/ACT scores?

I looked on a few colleges’ websites and they’re vague on whether they require all scores to be sent. I took the SAT and wasn’t happy with my score, but then took the ACT and got a higher score-- I want to send this one. I also took a couple of subject tests that I want to send.
For UC’s, they require all SAT scores, so if I sent my subject test scores, would I have to send my SAT and would I be at a disadvantage if this score was lower?
Also to clarify, for schools that only require SAT or ACT scores and are optional for subject tests, I can just send my ACT and then only subject tests?