I know you know this but the highest priority pilot (setting aside FAA, etc.) is an AS pilot on company business (i.e. new hire on observation flight) and pilots agreeing to give up their deadheading seats in the back. Apparently this is the culture at Horizon and some have carried it to Alaska.

As far as commuting, you have priority on AS but not Horizon flights. Priority is year of hire within other commuters. JS is first-come based on who checked in as a JS, so make sure you check in as a JS even if you think you’ll get a seat in the back.

Where do VX pilots fit? I got bumped by an AS pilot on QX, even though I was there first.

Since you flew on 04/24 you were still bumped by AS Pilot, starting today 04/25 you have the same priority as any AS Pilot since you are officially one now.
It was in one of the Company updates..
No more ‘VX Pilot’, get used to it...

Probably a agent training issue. Were you using your new Alaska ID? If you were using VX id you probably were boarded as an OAL.