I have a 26" APQS Millenium and I don't use all the throat space. I don't feel like I have control to do a good job when my arms are stretched out. I mean I do almost all if not all quilting close to the front of the frame.
I think you will love your machine. 20 inches is a lot of space.
As for borders - until you are comfortable doing them in all different directions, just turn the quilt. Here is a link to videos
http://forum.apqs.com/index.php?/topic/16352-turning-a-quilt-video-series/
APQS has an active forum and you might get good comparisons there
http://forum.apqs.com/