I came to find out that my HS doesn’t put the UW GPA on a transcript, so would I need to self-report, or would adcomms calculate it themselves or just look at the letter grades for each class?
They recalculate it if they want to have it.
Colleges often recalculate based on their own criteria (ex. unweighted, only academic classes etc.). Don’t do any recalculations yourself. And your HS will send a school profile with each transcript describing their grading system, class levels, etc. so it will be clear to college adcoms how the GPA on the transcript was calculated.