The planet defenses thing I already addressed in the thread named "
Planet Defensibility" (<- Click there), so rather than post the same stuff in two places I'll just link you there and address the other thing here.
That's a characteristic almost exclusive to the Nebula and other New Class capital ships; it's not representative of any other ship, and keep in mind that ship limits cannot be applied to individual ships and therefore must be large enough to allow appropriate numbers of everything. We can't say, for example, you're only allowed one Nebula but you can have 10 MC80Bs. Also, discussions of ship numbers in Star Wars are very inconsistent and unreliable. Plenty of times that sort of fact or stat is thrown in as a minor trivia thing, despite the fact that it doesn't really make sense within how star Wars works. Otherwise, the New Republic spent tons of money on the New Class Modernization program which by all counts was effective and we have no reason to believe the results of it were prohibitively expensive, and yet just ditched every capital ship and went back to spamming older models of Mon Calamari capital ships as they were fighting the biggest war in their history just to keep some aspect of "ooh look how unique these are!" When the Imperial fleet is mentioned, Thrawn having only 200 ISDs was considered pitifully low even for the 8 sectors he controlled, and that's just an individual class.
As for how this translates into game mechanics, aside from what I already mentioned, it's relatively scaled and ship numbers in the mod are actually fairly similar to Sins, with some different scaling based on the faction. There's a higher number of capital ships than Sins, yes, but that's because there's not the same sort of hard divide between Frigates, Cruisers and Capital ships as there is in Sins; it's more of a spectrum. In Star Wars, the best frigate may even be more combat effective than the worst capital ship (Compare the BAC to the MC80, for example). We're also only given one setting that has to apply to every map, so you'll have the same pop cap on Deep Core Conflict, a 16 planet map as you will on Dissolution which has 184. We tried a few things to make the pop cap scale off of planets as opposed to just research, including an EaW-style method, but none of them were successful. In these situations, if you want fewer ships on the smaller maps I'd suggest using the "Small fleets" option in the game setup screen.