Isn't all Enclave tech pre-war except for the power armor?
Not all. In fact most isn't. But a major point is that regardless, the Enclave had a hand in its initial development ie. Plasma rifles were created by both Enclave scientists (the MLPX Novasurge Plasma Pistol) as well as through contracts in the military industrial complex (REPCON).
Post-War Tech for the Enclave however, also includes Vertibirds (fully developed on the Rig), APA (as you mentioned which includes variants such as Hellfire Armor, Telsa MK II and APA MKII), Urban Plasma Rifles (developed by REPCON but fully developed by the Enclave), Hellfire Incinerators, Photonic resonance barriers, mobile light-weight defensive structures, and Enclave Mindcontrol devices (for uses on Deathclaws). Not to mention their developments in the chemical sector with both the Curling-13 Virus and later the Modified FEV virus.
We can also assume, given these sorts of developments, that the Enclave has been conducting vast amounts of research into various fields. Thus their scientific knowledge is far greater than what the Brotherhood possess. More than likely there are various technologies that they posses which haven't been revealed yet either.
Besides this, a major point is that the Enclave can manufacture all of this. Post-War.