The duo from TuksSport High School in Pretoria, who will represent South Africa at the Rio Olympic Gamess next month, coasted to victory in their respective races on Day three of the global age group showpiece, progressing as the fastest two athletes.
Munyai clocked 20.40 in the opening round in the morning session, and later eased off near the end of his semifinal to cross the line in 20.54.
Leotlela, who finished fourth in the 100m final the night before, produced times of 20.63 and 20.58, also coasting into the medal contest to be held on Friday evening.
In other races during the evening session, Tamzin Thomas and Gezelle Magerman were eliminated in the penultimate round of their specialist events.
Thomas finished sixth in her 100m semifinal in 11.71 and Magerman, who won gold at the 2014 Youth Olympics, ended fourth in her 400m hurdles race in 58.76.
