In my 5D3, I shoot AV or M in RAW and can set the Picture Style to Monochrome so everything I see is B&W. How do I do the same with the M5? Everything I see referring to Monochrome are special setting outside of AV and M.
It depends. If you are in Live view mode, you just hit the Q "SET" button in the center of the control dial (or on the screen) on the back of the camera. Then turn the dial to select Monochrome. If you want you can also tailor one of the "1" "2" or "3" settings to a different monochrome style.
If you are on the screen where the different functions are all displayed (black screen), then you have to select the picture setting on the left side middle (it's a square with a letter or number in it). Then you can change the style to things like Landscape/monochrome/user preset etc.