IPv6 M and O flags

Also, which is the recommended configuration.

Hi,

M = 0, O = 0  : Client uses RA to get non-link-local address and other settings. Even DHCPv6 server exists, client ignores it.
M = 1, O = 0  : Client uses DHCPv6 for both address and other configuration settings. This combination is known as DHCPv6 stateful. 
M = 1, O = 1  : DHCPv6 is assigning stateful address to client. If RA includes network prefix, client also gets stateless address.
M = 0, O = 1  : Client gets stateless address from RA. DHCPv6 only assign other configuration settings to client. This combination is known as DHCPv6 stateless.

Which will you use will depend on your network scale and the design you choose.

I recommend you to read the RFC to have a better understanding of this topic:
https://tools.ietf.org/tools/rfcmarkup/rfcmarkup.cgi?draft=draft-ietf-ipv6-ra-mo-flags-01.txt