Aft cg makes both worse as it reduces control power while not affecting the engine moment (for Vmcg it reduces nosewheel steering effectiveness as well as rudder power, even though the former isnt counted for cert anyway)
Weight classically makes Vmca worse as it reduces, not due to the dynamics effect mentioned but because of the 5 degree bank limit. The lighter the aircraft, the less sideslip is a result of a 5 deg bank and hence the less restoring yawing mom,ent can be generated to help the rudder.
Weight is nominally neutral for Vmcg.
(Note that Ive seen items from Airbus arguing for weight neutrality or for heavy weight critical for Vmca, based on the assumption of a fixed lower speed limit for Vmca and hence arguing that the higher AoA at heavier weights reduces control effectiveness more than the sideslip helps. An interesting idea, and obviously type dependent. We always test at min weight for Vmca, though)