...If my mash and brewhouse efficiencies were equal then it would be easier to make adjustments after my preboil reading.
If the brewhouse ('total') and mash efficiencies are different, it means that BeerSmith (or any other program) is trying to account for volume losses after all the wort is in the kettle (other than evaporation).
I have better consistency (and understanding) throughout the brew if I concentrate on efficiency in the mash and assume some constants in the kettle.
In BeerSmith, total/mash efficiencies are different if you enter volumes for losses under "Boil and Fermentation" in the "Volumes" tab. Delete trub loss and kettle top up, and just assume those as constant when you set your batch volume.
In your equipment profile setup, set a constant mash efficiency. Also set your lauter deadspace: amount of water it takes to fill your mash tun to the top of the manifold.
If this doesn't make sense, let me know. Lots of coffee today