With SLAAC , it works
Packet sniffer and RouterOS logging are your friends, I’m sure there’s an explanation.
Well what happens is that :
If I say I use SLAAC (managed=0)
My Windows hosts uses SLAAC just all right, but has no DNS
If I say I use SLAAC (managed=0) and want to provide DNS throught DHCPV6 (other=1)
My Windows hosts uses SLAAC just all right, but still has no DNS : it performs no DHCPV6 request at all to my router
If I say I use managed DHCPV6 config (managed=1)
My Windows hosts still uses SLAAC not performing DHCPV6 requests. Mikrotik still sends the A flag in Prefix Information, which means SLAAC should be used. My host then receives two opposite meaning messages, and the stack then assumes SLAAC, and does not perform DHCP requests.
If I force a DHCP renew on my host
Whatever network IPV6 config, if I force my Windows host to an address renew , it then performs a DHCP request to my Mikrotik, but that one does not answer, and logs “handling only prefix delegation discarding”
Please, have a look at that presentation which gives some details : http://www.swissipv6council.ch/sites/default/files/images/ernw_ipv6_behavior_conflicting_environments_20150430.pdf
Confirmed 
I can’t test things right now, but:
It works here, it’s the simple example I posted.
If you don’t like A flag and you didn’t configure prefix manually in “/ipv6 nd prefix”, you can disable it in “/ipv6 nd prefix default”.
Nice presentation by the way
To clear some things up:
Full DHCPv6 is coming. sorry no ETAs, now with this out of the window.
Windows in any form do not support DNS via RA (or SLAAC) you can do whatever you want - MS Windows will not take the address in the advertisement. That is why at the time DHCP-PD server was made to answer to DHCP INFO packets (well, they are part of DHCPv6). For that to work you have to advertise to your network that there is “Other Configuration option” and that tells all the IPv6 hosts that they can ask for stuff. If you start to advertise - “managed configuration” flag - that will tell every host on the network NOT to use SLAAC for auto-configuration. However, you will still see the advertisements on your network. That is because hosts (the end user nodes of the ipv6 network) need to be told what policies are active in the network.
Ok thx for informations