At the P School, or just the P, you'll get exactly what you would get if you were still enlisted. Once you become a cadet on the hill, you'll pay back all the money they charge you for your initial issue of stuff, and then you will receive normal cadet pay. Cadet pay was 800 bucks a month a few years ago. I think the Hap class got $115 a month until they paid back initial issue.
As far as Active/Reserve status, you're still active as a preppie, but your status will change as a cadet. The Academy cadets are technically in inactive reserve status. This means that the time as a cadet won't count toward O-1E or Time in Service. If you are in the Goldilocks zone where you hit four years and one day while waiting to become a cadet you will be the rare USAFA grad with O-1E pay.
The date I initially enlisted and the date the Air Force considers my pay date are different because they offset the years I was at the Academy. They just made up a date that made the time work
Congrats to those who made it in to the P school. To those going direct entry, brush up on algebra, chemistry, and physics. The first year coming straight from the operational Air Force can be tough academically.
-Good Luck