Thomas and Harries have quite recently played for Wales Under 19's, have both been regular starters in the 21's this season as well as the 18's. Harries has also been captain of the 18's since Maddison moved up to the 1st team
Both very small in stature and against Man City, who were physically a very big team, found it difficult to retain possession. But they may be better suited playing further up the pitch rather than at full/wing back.