I am a 7Dii owner as of last when I replaced my 7D purchased from new. As the 7Diii has been dropped I do see any of M model of cameras as a replacement. The AF is just not quick enough and M6 mki or ii not having a evf the focusing via live view will be challenging to say the least.
The the M range use M lenses which means a sell EF mount and buy M or get the adapter.
As I own a sony NEX5R and have fee e mount lenses I have borrowed a friends sony A6500 using a sigma mc-11 adapter to mount my canon ef glass to the A6500.
IMO the IQ is better using the A6500 than my 7Dii. Because 20.4mp 1v 24mp, no AA and low pass filter on the A6500, better sensor and processor give a much better IQ IMO.
For me I will not be buying any canon mirrorless camera instead I be waiting for the successor to the Sony A6500.