UC only considers you a transfer applicant if “you enrolled in a regular session (fall, winter or spring) at a college or university after high school”, according to http://admission.universityofcalifornia.edu/transfer/index.html . I.e. taking college courses while in high school does not cause you to be a transfer applicant.
In your situation, it is still likely better to enter as a frosh, since you will have the option of taking the full four years to graduate, or accelerating your graduation if you want to and the college courses completed while in high school meet enough requirements to allow that. Entering as a transfer means committing to a major now, and requires that the college courses completed while in high school meet the specific general education requirements and major preparation requirements for your target campus and major (which high school students taking college courses usually do not plan for when choosing courses).