As per CPs,
A player fleet will be 6000, or 7000 CP if they use the bonus in the leader trait. This is enough to field an IDS fully loaded. This is pretty much identical limit to GCWII.
But now, players can ALSO take their PDF fleet ships along in their main fleet when they want to - and on those units they pay no maintenance, either.
A system can add a few smaller ships each, and then players have the choice of using their CP for their player fleet on one big unit or smaller units, too. You actually have MORE ships in GCWIII to play with.
In terms of math (as far as combat goes), this isn't the case. I don't believe combat math has changed at all. Math for setting up your fleet (a one time thing), might be more involved, but it also results in a more fair accounting for what players have in their fleets.
Before you had units like ISDs with massive ground contingents and full of TIE Advanced costing the same CP as weaker vessels in the end because we didnt take into account onboard units fairly. This new way of looking at it accounts for how you set up top to bottom -> if you set up an ISD with TIE Fighters, and "cheap" aux and troops, etc, you can probably use the leftover CP for another small support ship or two. If you want to be that guy who loads it up with 6 TIE Defender Squads, 10k Royal Guards and 50 AT-AT ... well, its going to be very expensive, and probably eat up all if not exceed your CP limit