I weigh the whole beans before dropping them into the grinder. That is the number I use for the coffee water ratio. Always consistent, always right.
When I use dark roast beans I use a finer grind, I use slightly more coffee (per water) and a slightly coarser grind. There are reasons for this, explained better than I ever could here:
I am not familiar with the Breville smart grinder pro, but I do know many grinders have presets for different kinds of coffee drinks and different kinds of bean roasts etc., that adjust the grind and in some cases the dosage (per consistent measure of water). I like to avoid all "automatic" compensations the machine may provide, so as to take full credit for screwing it up myself.
So I would figure out a medium medium medium setting on the machine, and adjust the ratio of coffee to water, (measuring weight of whole beans) and the grind setting you like overall, for a medium or light-medium roast coffee. Then for a dark roast I would add a bit more coffee and grind it a bit coarser.
Confession - I used to think this XXXX didn't matter. But wow it does make a difference. Especially in a pour over. I haven't jumped into the espresso world yet. I am quite intimidated by it. But for pour over, I kind of have this figured out, and am able to perform it consistently. I am not ready to stray far from home.