I prefer to use the extra wide backs, but they have not always been available or out of my price range so have been piecing backs for many years. At least one of the ladies in my Tuesday group doesn't like the extra large backs at all -- they are "too big" even for her large projects and so she always pieces the back.
From the old days I was always taught to avoid seams right down the middle of the quilt due to folding and considerations like that. If your fabric was wide enough that you only needed two widths, you had one width that was full down the middle, and then the other you split into two pieces, with one half width on either side of the full widths. Back in the days of 36" wide yardage, it was three full widths of the fabric going horizontally for the typical length.
As the others have said, yes, 1/2" seams. I press open as I always do. I always use a rather small stitch as someone who presses open.
As time has gone on, I've begun incorporating more fabric/seams in the back, often including orphan blocks or fabrics that are related to the top but maybe too large a scale or other issues. They work/hold up just fine. I do prefer less quilting and a fluffier batting than is currently in favor -- perhaps that works in my favor
