Usually if you are a late to rate guy/ girl or Captain and above you don’t have to stay on base. Most training pipelines have their in processing guides readily available online as well.
Assignments start being worked by AFPC after public release.
Don’t know how true it is but what I heard previously only the number 1 gets “bonus” points from the board. You can be number 2 and the number 3 can get rated higher if the board values the other components of their package more than yours.