Spurs won today's early kick-off 2-0 at the Etihad with Johnson and summer arrival Joao Palhinha scoring on the day.
Johnson said afterwards: "Really pleased.
"I thought we played really well today, and we built on what we did last weekend. To come here get a clean sheet and score some goals - perfect."
Asked about the differences between manager Thomas Frank's methods and predecessor Ange Postecoglou, Johnson also said: "Nothing massively.
"Two different coaches. Really enjoying it and a lot of detail goes into the set-pieces, but at the same time he gives us a lot of attacking freedom.
"The first few games we have kept two clean sheets and against Man City it is not easy. I have played here a lot of times and conceded a lot of goals."