One of the bigger changes is that Cryptexs and Necron Lords now occupy an HQ slot of their own. For every HQ character in your list, you are allowed to take one of the new Cryptex/Lord detachment (ala warlock council) which is between one and five characters each.
The old royal courts we know and love are gone, but are now a formation (Aptly called a Royal Court) consisting of an Overlord, 1+ Cryptexs, and 1+ Lords.
The Overlord may not take a Command Barge, and all the characters are clumped into one unit.
+1 to reanimation protocol (which is not going away or changing) which stacks with a resurrection orb, and some other buffs that I can’t remember, but one had to do with phaerons (Oh, and any phaeron in your detachment MUST be your overlord).