If I have taken 3 SAT II's but a college recommends/requires sending 2, do I have to send all 3?

Or can I choose which 2 to send? What about if a college has opted out of the “score choice” system? Let’s say I took 3 subject tests, scored high on 2 but low on the 3rd one. If a college recommends sending 2, could I just not submit the 3rd score? And for the colleges that aren’t part of “score choice”, would the same apply? Or would I have to send all 3 even if they recommend 2?

Thank you in advance!

It depends upon the school. Few schools, even if they require all SAT scores, require all Subject Tests. You can look at the following thread for a start:
http://talk.collegeconfidential.com/sat-act-tests-test-preparation/1912440-must-you-submit-all-sat-act-or-sat-subject-test-scores.html#latest

Not that testing requirements have been very fluid the last couple of years, so check with your target schools before sending your scores.

Agree. You need ot read the details for each school you apply to. There is no shortcut.