Ok so I don’t have a diagram like you asked, but it looks like neither does anyone else and the principles are pretty easy to grasp so I’ll just try to lay them out. Maybe someone will come through with a diagram.
You got your hub with one bearing on each side. Between those two bearings, running through the hub, there must be a spacer. The spacer must be the same diameter as the inner race of the bearings and make contact with both of the bearings.
On one side of the wheel you prob have a brake plate. Between the brake plate and the bearing there must also be a spacer, and this spacer must also be the same diameter as the inner race of the bearings. If the spacer isn’t big enough, the brake plate will press or rub against the hub, binding the wheel, and you have to move it out further. Just stack a few washers on top of the spacer so they’re up against the plate and not against the bearing.
On the other side of the wheel you may have a speedo drive. The same rules apply here: use a spacer against the bearing that has the same diameter of the inner race of the bearing, and if necessary a washer or two against the interior of the speedo drive.
If one side of the wheel doesn’t have an accessory like a brake plate or a speedo or whatever, you’ll still need some kind of spacer to fill out the distance to your fork or swing arm. You guessed it, this spacer must be the same diameter as the inner race of the bearing. (For some applications it may be possible to use a special nut or thick spacer that has a narrow or cone-shaped side designed to fit against your bearing.)
The point of all this is that a line of force from your axle nuts should always go from one side of the wheel to the other through the inner races of your bearings, which are supported by the long spacer through the hub. Stack up washers or nuts or whatever however you want, or however is necessary to center your wheels, as long as the pressure against the bearings is on the inner race only.