The pair arrived in the final days of the summer transfer window as Wenger splashed £52million to reinforce his squad ahead of the new season.
Asked how the pair had settled, the Frenchman said: "Very quickly and very well, but the real test is the games so we will see and know very soon.
"What they do in training is promising. They have the focus and the quality in training that we expected and on that front I'm very happy."
Wenger added: “Mustafi is young but he already has lots of experience, international experience.
“Perez is versatile, he can play on the flank and through the middle of course.
“Not only can he score goals but also provide a good number of assists.
“He is versatile and has some interesting qualities."