1. As Revanchist says, the ships with anti-fighter capabilities are a lot more fragile, but also the NR ships in general tend to not be as good at direct ship-to-ship combat. That amount of lasercannons (which are taken from canon armaments) is offsetting their ability to put out damage against larger ships, so while they do have better fighters, they still typically have less of them, and those fighters/bombers to some extent have to make up for deficiencies in their fleets to an extent that the other factions don't need. For other factions, you still tend to have the potential for a lot more fighters (both in command and supply), so fleet tenders are fairly important, especially for the PA.
2. The amount of fighter supply is determined by canon amounts of fighters the ships could hold. The amount of fighter command points (how many you can field at once) is standardized. Frigates/cruisers get 1 point, dedicated carrier frigates/cruisers get 2. Capital ships get 2, dedicated carrier capital ships get 3. The Venator, as a carrier cruiser, gets 2. The only difference is the numerical superiority ability, which we're removing from almost every ship.