DH & I have a king bed - we have twin size quilts on it and always have. This started because in the winter we still use the quilts my grandmother made for me as a child and teenager, so they're twin size. (And they are the WARMEST quilts in the world, made of wool and grandmotherly love!)
We got used to the two-quilt setup in the winter and it is really comfortable for us, so we do that year-round now. We're still under the same single sheet, but on top we have our own sets of quilts. Extra quilts are under the bed on each side so if it's an extra chilly night we can just drag another quilt out.
For making the bed, I have a thin cotton quilt that is oversized even for our king size bed - it's like a bed slipcover almost. (My first quilt, turned out way too big, lol) Neither of us care if the bed looks neat during the day so most of the time we just sling that quilt over the bed to keep cat fur out of it and call it good enough, but it CAN be made up neatly when we feel like it.