100% rigid and transparent.
You’ll join as the most junior F/O but you’ll move up the list fast, recruitment is at full speed at the moment. I’m not sure of the chances of starting on a long haul fleet, short haul is most likely. Because postings and promotions is seniority based if you’re going to join it’s advantageous to do it as early as possible.
Once you’ve done a few years the world’s your oyster, you can move fleets anytime after your freeze is up and sometimes before.