here is the spec sheet for this toilet. According to it, you would have 1-1/4" behind the toilet if you have a true 12" rough.
Yes, Toto bowls are made to fit standard and elongated toilet seats so most seats will fit them.
The CST744S#01 uses a g-max flushing system which provides a very strong and quiet flush. The CST744EL#01 uses a e-max flushing system which uses the same technology as the g-max but uses 1.28 gallons of water instead of 1.6. Also, the CST744EL#01 is a comfort seat toilet and sits about two inches higher than the CST744S#01.
here is the brushed nickel flush lever.
E= 1.28 gpf emax
S= 1.6 gpf g max
L or F means ADA height
Comfort height emans the seat is higher, around 17.25 inches high with the seat installed. High profile means the tank is a tall tank. Low profile toilets have a smaller tank for people who like the petite look or have a shelf over the toilet they need to fit under.