The clutch mod is one piece to replace the two piece back torque limiting feature (slipper) in the stock Busa clutch. The spring pressure goes up as the slipper actually provides increased pressure under load which no longer is present with the clutch mod. Generally speaking, other than the higher spring pressure you won't notice it being gone unless you drop it into a gear much lower than you should and let the clutch out with the throttle closed. You also won't see any advantage if you aren't getting clutch chatter. I've had bikes that don't need it, and one that absolutely needed it.
The lowering makes the bike handle differently. It doesn't like to turn as well but I am used to it. I ride the corners pretty conservatively so I really don't feel like I gave up anything. Lowering gives the feeling of riding "in" the bike instead of "on" the bike.
I went 9.60 on my 2005, stock wheelbase just lowered, strapped, exhaust, and air filter removed. I've been 9.20's on my Gen-2's set up similar (but with an air shifter). Others have certainly gone quicker with less.