Raking the rudders under the boat reduces the amount of weather helm you feel by putting more of the rudder underneath the pin... giving you more mechanical advantage over the weather helm... It doesn't technically reduce it....
as all the forces are still in play... Ya just can control them with less force...
Mast rake is the angle of the mast... Moving it forward reduces weather helm... Raking the mast aft increases weather helm... This happens because the center of effort or center of pressure is moved aft when the mast is raked back... The further back the center of effort is... The more the boat is going to naturally want to round up to "weather".. Like a wind vane..
On something like a H14 this is also useful because it moves the center of effort over the rudders... and with the lack of dagger or center boards you can decrease the amount of leeway (the tendency of the boat to slip sideways) by loading up the rudders... This causes weather helm... Which is also causes drag... But it has been proven the tradeoff is well worth it on a H14 or H16...
Watch a windsurfer steer the board... The tip the mast forward to fall of the wind and turn down... Or tilt the rig aft to head up...
Try it on your H14... With just your body weight and sail trim you can almost steer the boat with the rudders in the up position....