Llandovery's Chris Knight scored two tries with Carmarthen Quins duo Lee Williams and James Davies chipping in with one apiece while Cross Keys' Rhys Jones kicked three conversions as Wales pulled away in the second spell to win the tournament at the second attempt.
Wales Sevens head coach Paul John said the tournament had proved a worthwhile exercise as his side prepare for the World Series kick-off on Australia's Gold Coast next month.
"The tournament was just what we wanted as we had some tough games. Every one of the 16 boys was given a chance. To beat South Africa twice, once in pool play and once in the final, was very pleasing.
"We were invited to play in the tournament last year where we lost to South Africa so it was good to turn the tables against a very good side with quite a few familiar faces in it," he added.
Wales had earlier gone about their business clinically and efficiently, conceding a single try in a massive 40-7 victory over the Pumas.
Wales raced to a 19-0 halftime lead over the stubborn Zimbabweans in the semi-finals, but went to sleep for a bit in the second half, allowing the Zimbabweans to creep to within five points, before prevailing 26-14.
A Wales Development side lost the Bowl Final to Romania 17-12 to finish the Grand Prix series event in Bucharest in 10th place out of 12 competing sides.
The campaign got off to a promising start with a 14-10 win over Romania but successive defeats to England (40-7), Portugal(10-7), Georgia (24-7) and Italy (20-12) saw Wales drop to the Bowl.
Wales won their second game of the tournament in the semi-final with a 28-5 victory over Ukraine but Romania gained revenge for their earlier pool defeat by winning the Bowl final.