I have purchased 4 "ex display" ceiling fans without wall switches "they had missplaced lost them", 2 x 48" fans 4 blade "timber" and 1 x 36" 3 blade metal and 1 x 52" 4 blade timber, I'm told that I would have to buy the correct rated wall switch to suit each fan so as they run at the right speed for their size, I'm told that the capacitor in the wall switch is rated in micofarads, e.g. 4uf -4uf or 3uf and 4uf, what capacitor do I need to run the fans at their best?

Please tell us more about this purchase and the fans. The questions you have do not on the surface appear to be logical. Ceiling fans do have capacitors but they are a part of the internal circuity of the motor windings. Determining the correct size is an electrical engineering feat.
Wall switches would not have capacitors, not even remote controlled fans. A remotely controlled fan would have a transmitter (the remote) and a receiver and therefore not have a wall switch. The receiver of a remotely controlled fan may have capacitors but you would not be purchasing capacitors for it, you would purchase a receiver a long with the remote). Of course there are universal remote control units.

Tell us more.