What are the typical range of maximum braking friction forces?
What is the relative difference between hydraulic and cable actuated disc brakes? 
What is the relative difference between hydraulic and cable actuated rim brakes?

Generally speaking - hydraulic brakes offer more modulation.  There's more &quot;hand-feel&quot; between the initial bite and through to full-on braking.
Whether its disk or rim is less important - the rim brake can be treated as a really big rotor.
Cable actuated disk calipers tend to be single sided, so they have one moving pad and one stationary pad.  These can work fine, but they have to flex the rotor subtly when braking.  A hydraulic disk caliper, and any kind of rim brake will bring both pads to the braking surface.
A good rim brake can easily exceed a mediocre disk brake of any style.  Which is better between a good rim brake and a good disk caliper is still undecided.  Disks have a weight and aero penalty, but don't depend on a planar rim.