This is my rules:
If the selvage won't show through, I will leave it in and do 1/2" seam. Selvage edges don't ravel.
I personally don't think the direction matters on the seam unless you take it to a longarm quilter - then you follow their rules.
I'm not the greatest quilter so I go with a print that will hide my stitches. Same with thread.
Good luck! I'm sure it will be beautiful no matter how you do it.