If you run a custom gearing strategy, in some cases it can give you a tiny bit more accuracy around e.g. trinket and relic suggestions to pair with your currently equipped legendaries and specific talents.
In most cases, it's not really worth the effort.
To get more accuracy than the adaptive strategies, you really need to go down to the "bare metal" and do actual simulations. We'll be creating a way for you to auto-configure a batch of simulations from gear in your bags very soon if you wish to do this and let your computer crank to squeeze out that last bit of theoretical accuracy.