The idea of using different inserts is to keep the space around the bit small for added stability when passing small parts by the bit and some of those plates with removable inserts have one that will allow the use of guide bushings.
Some people have taken their collet wrenches and put a double bend in them so that they can reach below the table to change bits. I just pop my router and plate out of the table to change bits, much easier that way.
Someone I consider a master woodworker once told me that a master woodworker is not someone who never makes mistakes. He is someone who is able to cover them up so that no one can tell.