Mags interchange between all paddle-release P99, PPQ, SW99, and MR Eagle models of the same caliber, but the paddle-release mags do not work in the thumb-button PPQ M2.
The thumb-button mags only work in the PPQ M2. There are pictures illustrating the difference in the Walther M-Series Pistol manual I linked earlier.
Mags interchange between all paddle-release P99, PPQ, SW99, and MR Eagle models of the same caliber, but the paddle-release mags do not work in the thumb-button PPQ M2.