Does it matter which one I request? Do universities have a preference?
If you are currently in school and reporting in-progress courses on the application, you will not have a final transcript to show now. If you are admitted, the admission will typically be conditional on completion of the reported in-progress courses with high enough grades, to be verified by the final transcript when that is available after you complete those courses.
Your HS GC will send your unofficial transcript to the schools you apply to. Next spring when you choose a school and graduate HS, your GC will send an official final transcript to that one college.
To complete some applications you will also will need a copy of your six-semester unofficial transcript, as many schools have applicants input their courses and grades directly into the common app, SSAR, SRAR, or the college’s proprietary system.
Your initial transcript will be sent by your school counselor to the colleges you are applying to.
Your final transcript is sent after graduation.
Both are official transcripts and are to be sent directly from the school.
The school counselor should give you a copy of your transcript and some colleges are fine with an initial transcript being self reported. In the common app you list your courses and grades, they should align with your transcript. Sometimes the transcripts abbreviate course titles, but type them out in the common app.
If you drop a class or change your courses between submitting your application with your initial transcript submitted and graduation, you should inform the college.
Some high schools use Naviance or parchment to sent the transcripts. Makes it very easy.