I get a cutter for each caliber that goes inside the trimmer body and a case holder for each family that screws into the top. (Use a lock ring to return to your settings without having to reset it)
I have a cutter for 22, 24, 27 & 30 cals. Its a bit of a pain to reset the cutting blade itself exactly perfect, once its dialed in I lock it down and dont change it.
Each case family will need its own case holder. To clarify the case family comment, I can use my 3006 case holder to cut 270, I just set it up for 3006 and use a washer under neath the lock ring to make it the correct height so that it trims the 270 to the correct length. I use a different cutting blade between the two obviously.
Your 6mm cutter should work just fine for both dasher and creed. The cutter just spins around in a circle, anything of that diameter is fine to use.