How many co-processors is the limit to make crafting as fast as possible?

Right

And the mecontrollers what size changes?

Depends on what you are crafting. Or more realistically how many steps.

If you put one step of a crafting process per interface you can put a total of six assemblers per interface and you will need one co processor per assembler minus one. This is with each step of the crafting process having a dedicated interface.

So.....

("Crafting steps" × 6) - 1 = #CP

Taking a sword for example....
#1 log -> plank
#2 plank -> stick
#3 plank + stick -> sword

You would need 3 interfaces, giving you 18 assemblers. Minus one means for the fastest processing time you will need 17 co-processors and one crafting CPU.