I do custom and E2E and quite honestly I have never seen an E2E that looked bad on any quilt. Choose a nice blender thread and go for it. I have found that a sagey green or gold looks good on almost everything.
Regarding how you load it on the frame, as long as you have room on the sides to put your side clamps on and have a little spot to test tension and room to get at your bobbin there is no reason you can't load it sideways as long as your Panto isn't obviously directional. Most aren't and again, once quilted you would be hard pressed to notice it and a non quilter wouldn't notice at all. Given that the difference between length and width is only 10" I would be inclined to load it so that I have more room on the sides. If you load it that way you would only have one more additional pass to make.