I use these all the time for my domestic US travels.

Sometimes, quite randomly but not very often, they'll post as economy and it is a bit of a hassle getting BAEC to then re-credit them correctly. The last time it happened I had to send copies of booking emails from AA.com, boarding passes, basically everything I had that showed it was booked in F! Usually though it is no problem and they appear as 'F/F'.

Bookable through AA.com, as others have said, using the 'Instant Upgrade' option. The fare basis shows as 'KUPPMZ' or similar.

Avoid codeshare flights on Alaska Airlines (from a mileage perspective) as they earn no tier points. Mine posted to my BA account with no miles which by all accounts is wrong but it wasn't worth the hassle to chase up.