For the 4 pot and 2 pot brakes, do I need 25.4mm or 28mm rotors?
25.4 unless you change all the callipers .
25.4 on the OE 2 & 4, and also the smaller AP CP5040
28mm and you’re looking at either alcon or larger CP5040
The Lotus two pots and Lotus AP 4 pots use a 26mm disc from the factory. Both will work with the commercially available 25.4 discs
That is what I thought, thanks all for the clarification 
My APs on the front with factory 4pots are 26mm