To help you understand the UCSB decision a little more, 2 years ago the acceptance rate for Engineering there was about 15%. It was likely no higher this year. That is less than the overall acceptance rates at UCB and UCLA, so you can see how choice of major can affect your chances. Also, when a school such as the Engineering college says Subject tests are recommended, that should be read as “required”. That was strongly, strongly, strongly hinted at by a UCLA rep at a campus tour.
Good luck on getting off the waitlists if needed. We know kids who that has worked out for.