You have to remember that a booster of any kind is operating outside of the hydraulic braking system. It essentially is like just giving you a heavier foot to push the pedal. It's not changing the amount of hydraulic pressure being made by the master cylinder. Again I go back to what matters is the amount of force applied to the pads/rotor vs the amount of pedal travel.
To answer your other question about whether too small of a M/C piston would make the pedal low, I'm going to assume you mean it travels farther toward the floor, yes a smaller bore would increase the travel and make it closer to the floor but you would still feel a firm pedal as long as it were bled correctly and there were no air in the system. However there is a certain amount of limitation to the smaller M/C's leverage, if you will, so you would get to a point where your foot would feel a hard pedal but you wouldn't be able to make enough pressure. As the pressure you do make increases the more difficult it becomes to continue to increase it more. It goes back to the ratio of the M/C vs the Caliper piston.
I hope this is helpful & that I'm not confusing in my explanation. Please post what happens with the changes as you go. Good luck! -LW
