The military services all have their own ways of teaching people their standard flight skills, disciplines and approaches. Having a basic flight certification such as PPL in hand demonstrates the person has the aptitude, isn’t afraid to operate complex machinery in the air and isn’t prone to airsickness. After that, the military IPs I know (I was assigned to a Navy S-3 replacement air squadron [the non-deploying squadron that teaches new pilots and NFOs a specific air frame before going to their Fleet squadron]), including DH and DBIL who cycled through F-14 training squadrons as IPs back in the day, and two USNA sponsor family alumni who have been jet and helo IPs, all have commented it’s a challenge to “unlearn” bad habits and non-standard military patterns with some of their students. That includes re-calibrating mental attitude and over-confidence about flying experience, on occasion.
The needs of the military service will drive all, as always. There is simply no way to know at the SA and service ROTC how many spots will be open for any given year group. The whole person is looked at - academics, leadership, military aptitude, etc.
You want to be a good all-around performer who is ranked high enough to put you in good position to compete for aviation selection.
As mentioned, applying for Navy OCS is the only way to know for sure you are headed to aviation going in. There would still be competition to land an aviation seat at OCS. The Navy use OCS to cherry-pick exactly who it wants to make up annual intake numbers as needed to add to USNA, NROTC and other commissioning programs yield.
Back to the big picture - previous flight experience and certifications are in no way a negative. They are not a slam-dunk multiplier, though. First, the service evaluates your qualifications and performance to be an officer. Then the needs of the Navy and how that intersects with a midshipman’s desire to go naval aviation and the competitiveness of that individual across all aspects and against others requesting the same is evaluated.