Will Maggie 3.6 or 20.1's work in a 121/2 X 21 Rm

The 3.6 is better suited if you are looking to go the Magnepan route.

The short answer is yes, either speaker could work and sound quite good in a room that size. You might want to experiment with the ribbon tweeters being either on the outside or inside to get the best balance between focus/details and size depth/width of the soundstage. I have heard many Maggies sound terrific in similiar sized rooms. Hope this helps.

I had Maggie 1.6s in my 13 x 22 room and always felt they had too much output from the QR midrange driver. I used ficus trees to help dampen the reflections and it was pretty good but I think 15 feet wide would have been better.