I know I have a slight bias, but, I will try to be as un biased as possible here and only state facts.
1) Washers don't affect light but are different on the different buttons. They are one way to differentiate buttons if the are present. There function is actualy to be placed on the top of the control panel to slightly raise the buttons and allow them to be used in a 24 mm hole.
From the buttons I have ordered, Twisted Quarter, Jammaboards, and GGG supply the same version of the button. Twisted Quarter was using e-switch, Jammaboards and GGG were using Zippy's.
Twisted Quarter and GGG match the led for the button color, Jammaboards supplied white LEDs with their colored buttons.