Transmogrifier

I have a couple of questions regarding the Transmogrification and using the Transmogrifier. I am currently running Dragon of IceSpire Peak, and I want to bridge the story into Dungeon of the Mad Mage. I am currently running a Plus subscription, and I will have to upgrade to Pro to use the functionality. Am I better off to add DotMM to DoIP or add the necessary content from DoIP into DotMM?  Not sure what is better (I'm not concerned about easier, I just want to ensure all of the existing stuff doesn't get lost in transmogrification) Second to all this, once I have transferred everything over via the Pro subscription via the Transmogrifier, would I then be able to downgrade my subscription back to a Plus or do I risk losing everything? THANKS!

No idea which is large, or which choice would be less work. Second to all this, once I have transferred everything over via the Pro subscription via the Transmogrifier, would I then be able to downgrade my subscription back to a Plus or do I risk losing everything? The Transmogrifier is just a tool, and losing access to it doesn't undo the changes you have made with it. There is absolutely no worry for you to go back to Plus after having used Pro shortly.