I would set switch off all the YN622 for a moment. Then place cameras on manual flash by just switching on temporary the YN622 on one of the cameras. Then I would connect one camera with the flash. If it works well for changing the power right out of the camera, then I would switch on the second camera. normally by switching on the cam gets the settings from the flash as far as I did see.
My opinion is the camera menu for flash always the master. if you change any setting on the flash that will work but if you change afterwards another setting on the camera menu, your settings of the flash are gone. I always make my setup right out of the camera menu. did not try it out with 2 cameras.
Camera: 1Dx, 5D3, 7D2, 7D, 300D | Prime:14 2.8Lii, 24 1.4Lii, 50 1.4, 85 1.2Lii, 100 2.8Lmacro, 300 2.8Lii | Zoom: 16-35 4.0L, 24-70 2.8Lii, 24-105 4.0L, 70-200 2.8Lii, 100-400 4.5-5.6 Lii, 200-400 1.4x 4.0L | TS-E 24 3.5Lii | Other: 1.4xIII, 2.0xIII, YN600EX-RT, YN560iii, YN-E3-RT, YN560-TX, Lee