Miller has to be first choice full-back. He had a few ropey games last season, true, but IMO the positive more than balanced out the negative, especially with the more focused direction he received from Arthur. I would say that Miller just about turned out to be our best signing last season, just edging Croft, who had fewer negative elements in his game but didn't deliver enough performances worthy of his price tag.
For the sake of the team, Connor can bring quality to a number of backline positions. Conversely, we'd be wasting Miller's x-factor if we moved him on to the wing, or heaven forbid, tried him in the centres or the halves. We don't need him to learn more specialist positions at this stage in his career.