As Davey points out, the whole DA Microfiber System was really developed as just that - a system. But that doesn't mean you can never experiment and try to mix and match liquids and pads to your heart's content! M105 tends to work extremely well on the microfiber cutting disc, but it will create dust where D300 won't. Maybe that's a concern to you, maybe not. But we've seen all kinds of mixing and matching going on - as paint varies so does the exact mix that yields the best results. There is certainly no harm in trying the microfiber disc with M105 and you can always pick up some D300 later on if you so desire. On the flip side, we've also seen D300 work great on a foam pad in cases where the microfiber was too aggressive on more delicate paint.
It's also a good idea to use at least a bit of caution when removing the microfiber discs from the backing plate. Rather than pulling up just on the microfiber portion of the disc, grab the entire thickness so that you're directly pulling on the foam to pull it off the hook and loop attachment system.
DON'T do this: