How much definition depends on the school of rifle.
This rifle does not yet have the outline of the lock panel cut in yet. But this is basically what you start with before you cut the lock panel lines in. You can see some pencil marks where I'll be stabbing in the moulding line. I won't relieve the stock much more than .02 or .03" of an inch. Similar to the trigger guard moulding relief in depth.
Here's a top view, showing the slight relief up to the line. There is not a dramatic change in contour between lock panel and stock, just a slight lowering of the stock material leading up to the line. This is like doing a drywall tape job, you have to feather the relief way back, or it will look like the stock surface dives in toward the line.
Another stock before lock panel definition lines. (#2 gun)
#2 gun finished. See how the lock panel and wrist are running in parallel planes? The wrist does not dive under the lock panel.