Hello,
Thanks for you answers and video.
I finally managed to do the migration. Apparently, my setup wasn’t that simple in the end, though 
What I have:
- 2 CAP ac access points
- 1 old RB2011 to provide wifi for iot stuff
- some VLANs to isolate trafic
What I did:
- uninstall wireless package from my CAP ac and replace it with wifi-qcom-ac
- migrate configuration from /caps-man to /interface/wifi
- migrate 1 CAP ac => failed (because of VLANs)
- read multiple times http://forum.mikrotik.com/t/capsmanv2-with-wifi-qcom-ac-and-vlans/171966/1 (took me some time to figure out my answer was there, but I didn’t saw it at first)
- a lot of back and forth
Finally, after having fixed my VLANs issues, I got my 2 CAP ac working well.
I kept the /caps-man in place for the RB2011 which is unsupported by the new /interface/wifi command.
VLAN support is a bit weird when we come from CAPsMAN v1, but all in all, it works pretty well and in an intuitive way.