My pre-boil is 7.1 gallons for 5 gallons finished.
-1.1 boil off
-0.5 for the kettle
-0.5 for the fermenter
=5.0 (sometimes)
I add an additional .55 gallons for every half hour of additional boil time.
Pre-boil is really what works for your setup. Wind, temp, kettle size, and more affect your boil off rate.
I would interpret "strain and sparge" the same as you. I never did that when I brewed extract with grains. I simply used the dunk/tea bag method and allowed it to drip over the pot.