The standard US board comes with 2 controls, 1 alt, 1 alt/option, 2 windows/apple command keys. Out of these 6 keys you would use your 4 preferred ones (and then have 2 spares off the keyboard). For example, I use the 2 controls and the 2 alts (one of which I use for AltGr).
I have a white WASD key and do see a brightness difference, but my white kinesises range from 5 to 18 years old and are possibly yellowed. There may not be a big difference at all with a new set.. However to be safe, I wouldn't use WASD white keys next to kinesis white keys, but if one type is in the thumb area and the other type is in the keywell area it should not clash at all.