Ground effect occurs at a height of approximately half the wingspan above the ground and becomes more of an issue the closer the wing is to the ground so high wing aircraft suffer less from the effect as the wings are always further from the ground at the same stage of flight as a lower winged aircraft. Also the F50s wing isn't very swept, thus decreasing the amount of drag created by wing tip vortices, and therefore decreasing ground effect.
With regards lift, high wing aircraft are able to produce some lift from the bump on the top of the fuselage at the wing root. If you look at the 146, the bulge on the fuselage produces enough lift to negate the use of leading edge flaps or slats at low speed, less weight from all the mechanisms etc.
Also, high wing aircraft are more laterally stable (due to wing angle of attack in a crosswind situation) than low wing aircraft hence why aircraft such as the 146 have anhedral to destablise them slightly and prevent dutch roll. The F50 doesn't seem to have any an/dihedral so it's high wing is "naturally" stablising but not sure about possible increased susceptibility to dutch roll (?)