ArchaicArcane ... I agree with most of what has been said. For your wrinkles, become best friends with Best Press. It will help to take out those wrinkles, plus give a nice light starch to it. You will find that you won't have the scorching problem you can have with the other types of starches. I've never tried the vinegar/water mix, though to answer your question, I would think it will not give you any starch/sizing back into your fabric. Just a moistener to provide some steam to take out those wrinkles. I really wonder if it would do any different than just spritzing with water only.
I'll also echo that the quilt to bed sizes are totally personal. Some want it to hang to the floor. Others want it just over the bed top. Then there's the thickness of the mattress, and as you mentioned your duvet will add some height too. My bed is a double antique ... my best fit quilts are 110" square! So, by the charts that's a King! The chart sizes would be way too small for my bed. Though I will say that it is multi-purpose as both the bedspread and a functional quilt.
And yes square ... I find that works the best for me!!
Good Luck ... and make it so it's what YOU want for your Alberta winters!!!
