how to setup bathtub spout and shower head in separate locations
Hardly any noticeable difference; though a "high flow" showerhead would make any difference WORSE, not better, as well as increasing your water use needlessly.

The water is already traveling through many feet of pipe to get to the bathroom. Whether there's 4 more feet of pipe to the showerhead or 9 more feet of pipe to the showerhead makes very little difference, particularly at the typical 2.5 GPM flow. At a more efficient 1.5 GPM flow, even less.

4 feet of 1/2" plastic pipe @2.5 gpm = 0.625 feet added head. (0.27 PSI)

9 feet of 1/2" plastic pipe @2.5 gpm = 1.406 feet added head. (0.61 PSI)

4 feet of 1/2" plastic pipe @1.5 gpm = 0.243 feet added head. (0.11 PSI)

9 feet of 1/2" plastic pipe @1.5 gpm = 0.547 feet added head. (0.23 PSI)

There's also no particular reason to put the valve set closer to the spout - so you could just put the longer pipe on the spout, and take advantage of the pipes in the shower wall.