Mustafi comes in from Valencia and Perez from Deportivio, reportedly for £35million and £17m respectively.
The Gunners boss said: “We have bought two players in Mustafi and Lucas Perez. We have a good little break now and we can help them to join the squad.
“Lucas Perez is not in the Spanish national team so can join straight away but for Mustafi we have to wait until after the break because he goes with Germany.
“I don’t think so. First of all we have a very big squad and we’ve spent a lot of money as well. We had to work very hard to get these two signings done.
I expected it to last until Tuesday but fortunately it unlocked very quickly on Friday. We don’t have any plans for anyone else now.”