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You can make up a few batches starting from 23gr to 25gr in 0.5gr increments and see which performs best for your rifle. Just check the reloading books/websites to verify the numbers before loading them up.
Any of those powders will work. Loading for an AR-15 is pretty simple, they're quite forgiving as long as your powder is suitable for the projectile weight.
I use h335 with the 55 grain campro. No crimp. Not sure your powder throw method but h335 will meter a lot nicer than varget. My 550b throws h335 bang on almost every time