Many,many factors play into the amount of rudder that needs to be applied during takeoff.
In the real world an aircraft equipped with say, a 100 hp engine and then modified with a 150 hp, will react much different on takeoff than one would think.
The size of the prop does make a difference, but in general it is how fast it spins in takeoff (rpm) and pitch. The defult setting in AH is high rpm, what you want during takeoff. As far as P-factor, design of the aircraft can also play a big part, if you have a big tail surface, you may need more rudder,conversely the large rudder will have more effect at slower speeds.
Best way to put it is every aircraft in here is a little different, just need to figure each one out.
A good way to do this is to start auto-takeoff and then move the controls a little bit to gain manual control. Do this closer and closer to initial takeoff as you get better.