Should I be doing these in some kind of specific order or does it matter at all?
And what is there after they're all done? Can I repeat them at level 30?
https://www.flickr.com/photos/155399.../shares/1Bm50w
no order, you can continue playing after level 30 replaying all missions.
only advice - defeating sueno has 2 different debriefs. 1st time its always the same (you can do the final mission once you defeated 2 of the branch bosses), 2nd time you get a different animation if you have a 100% completetion on the regular story missions.
the only difference after completing the game more rebels driving around and no intel gathering missions.