Castillo would immediately be the Best SP in the Braves organization.
He currently relies a little too heavily on a flat 96 FA, and would probably be even better if he leaned on his 96 SI with 70 grade movement more often. The SI is something like a grade 70 pitch that generates something like 70% grounders, and for some reason he only uses it 21% of the time.
I think Pache is pretty clearly the best prospect in the system, but if there was any trade where it would be OK to use him it would be for a guy like Castillo. I think Pache is pretty much off limits, but if AA can get Castillo for Waters plus Anderson/Wright and some other filler he seems like a guy who's just a pitch usage tweak away from being a true TOR guy. Maybe they would have interest in Riley, but with Suarez and Senzel it's less likely they they would want Riley.