How and when use the following parts? How does it affect the behaviour of the car?

AM18-1: AM18-1 - for shortening of the upper arm. It increases the camber gain at up travel of suspension and reduces the roll of car also.

AM26: AM26 should be used with AM06S on the rear suspension. It gives the possibility to have very low roll center at still good level of camber gain.

AT21S: AT21S has 0.5mm lower ball height than AT21. It extend the range of roll center setting.

AT28: AT28 - precise metal axis for 10T gears inside of geardiff.

C06: C06 - carbon version of AM19 for old A700 cars. I don't recommend it for A700L and A700EX cars.

ST24: ST24 - steel replacement of AT21 for suspension's links. ST24 has 0.7mm lower ball height than AT21 and provides increased operation angle for P13 ball ends.

A700-IAS and AM20: A700-IAS provides increased Ackermann setting but reduces max steering angle. AM20 should be used as the component of A700-IAS.

How better are P18/P19 than original P01/P02?
P18/19 are shorter than P01/P02. Material of P18/19 is more hard and fragile.