Motor recomendations

I have a DJI f450 that has been upgraded with extended arms now my f450 is an f550 with sill 4 arms. With first test flight it is more stable and response is quick. I was wandering if I could use a different motors with longer props to make it even better. Use of my copter is for arial photos with my Gopro with gimbal, next FPV.
Any suggestions?
My understanding is lower speed, longer blades (because wider arm distance) with a pitch of 4.5 or 5.0. I know there is a math to it but the basics is that it?
 

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