Former USAF officer & fighter pilot. … But I only made Captain (O-3) during my 8-ish year career and I came from ROTC. So I don’t have personal experience of the high ranks. Here’s my take FWIW …
*Right now *the Generals in charge are mostly former fighter types. It’s called the “Fighter Mafia.”
But in the 1950s-1970s it was mostly the bomber guys who were in charge; being a fighter pilot was not the route to 4-star Generalship. Over the 1980s the fighter guys slowly took over.
I suspect that in another 10-15 years it’ll be some combination of cyber & space guys mostly at the top.
USAF will always prioritize operators over support staff types for the high leadership roles. So personnel officers and maintenance officers won’t make the very upper command ranks. But there are still 1-star and occasional 2-star Generals from those specialties who’re in charge of that whole silo. The logistics guys are another support specialty with some heavy hitters on top.
As to Academy vs. ROTC vs. OCS …
The academy guys have a head start. Promotion through Major (O-4) is pretty much pure merit based. The higher levels O-5 & even moreso O-6 depend more on who got the best jobs along the way, which often has an element of who knows who. The Academy guys spent 4 years living with the generation of officers just ahead of themselves. So they know best who to call to ask for the next good deal.
Having said that, the pyramid is pretty steep. Of every 100 2nd Lts, only a few (5?) make full Colonel. And of every 100 Colonels, only 1 makes 3-star General.
So at the serious high ranks, your work to date matters a heck of a lot more than how you entered the USAF 20+ years ago. As well how good you were over those 20 years at making friends, getting the good jobs, and excelling at them. Unlike in the civilian world, screw-ups and timeservers don’t survive. But you only get to the high levels by having fought a lot of competition for the plum (read high degree of difficulty) jobs. Guys who are politically or socially clueless get left behind early.
As to one ROTC program vs. another there isn’t really a difference qualitatively. But the same political headstart that attaches to Academy grads attaches (with less strength) to grads from large ROTC programs vs. small ones.
IOW the Academy grad was exposed to 4000 schoolmates of his/her year and the 3 above. And built his/her entire social life amongst those folks for 4 years. The Texas A&M Air Force ROTC grad was exposed to (WAG) 700 schoolmates of his year and the 3 above. And he/she built much of college social life amongst those folks.
I went to USC. We graduated IIRC 20 USAF officers a year, so our total program was about 80 cadets. At a university which then had 6000 undergrads. So although I knew many of the other cadets and they knew me, by and large everyone’s social group was much more the civilians than other cadets.
An interesting aside is that a place like A&M or Citadel might have a head start over the Academy when it comes to inter-service connections which are a huge part of the upper reaches of the Pentagon. The typical A&M grad going into the Army or Air Force would have much better cross-service connections than someone from West Point or USAFA. I don’t know anything about which traditional military-oriented civilian colleges have significant Navy presence.
As to enlisted going to OCCS …
At least Air Force OCS now requires a 4-year degree. That wasn’t always true, and most movies talking about sending enlisted men to OCS were set in Korea or before.
Nowadays a sizeable cross section of the enlisted force has some college, and bachelor’s degrees are pretty common amongst the more senior enlisted.
I don’t have any recent stats, but I’d bet a few percent of each OCS graduating class is prior enlisted. I’d be surprised if it was more than 15% though.
One last point …
I was talking about USAF above. I don’t know for sure about the situation in the Army or Navy, but I imagine the broad outlines of these issues are the same. Whether over at Navy it’s the submariners, the surface guys, or the carrier guys who’re on top now would be an interesting question in it’s own right.