England, who host Lithuania at Wembley in Sunday's World Cup qualifier, played with a 3-4-3 formation at Dortmund in Southgate's first game in charge since being appointed full-time manager in November.
Southgate believes the squad at his disposal is comfortable switching formations to counter the opposition's style.
"We have to reflect on a very good performance," the former Middlesbrough manager told BBC Radio 5 live.
"It was a good way to impose ourselves on them, to have attacking positions which could cause them problems and that's how it panned out.
"We have exciting wide players if we want to play with wingers, and it's very much horses for courses. We can see the strengths and weaknesses of the opposition."
Liverpool midfielder Adam Lallana said the new system brought more balance to the team, saying it allowed the players to "express themselves."
"Ultimately, Sunday is the most important game and we will have a good game-plan to attack that game," Lallana added.
"There is a lot for me to improve on, I enjoyed the system. It allowed individuals to express themselves in areas of the pitch where they felt comfortable."
With three wins out of four games in the World Cup 2018 qualifying campaign, England are two points clear at the top of the group F standings.