I don't have a Canon printer, but I was trying to get some nice writing on a NFSC with RI. I thought I might get frosting sheets, use Kopycake fine markers and write my own saying on them and then put the FS on cookie with RI. I figure I can keep my writing much neater on the FS rather than on the RI. 2 questions:

Is that the easiet was too get it on the cookie? AND

If I write with the pens, will the ink run when I mist the RI with water to adhere the frosting sheet?

I can't answer most of your questions, but I would worry about the edible pens bleeding when then get wet.

I've attached icing sheets to RI covered cookies by "painting" on a little bit of corn syrup around the edges. they stuck perfectly. That might be an alternative for you that wouldn't make the pens run....

The only thing I can say about your FS, use vodka or tequila with a small paintbrush to apply it (brush the dry RI) ! It's evaporate way more quickly.