Not quite sure what you are looking for here. But, to answer as best I can:
If you have a preset that expects a stereo input and you give it mono, you will probably lose something. But, you could use the routing to feed the mono signal to both stereo inputs. Probably all depends upon what you are trying to do.
If you don't have enough audio connections for what you are trying to do, you may not get the best results. This should come as no surprise. But, again, you can use the routing to parallel inputs or mix outputs to give you the best results attainable with what you have.