I got the OC200 to adopt the R605. That was fine.

The DHCP pool set up is different. On my MikroTik I have a range of ...100-254, and I set static IPs outside this pool. This is what I set on the controller. However I was not allowed to statically set any devices outside this range. So I set the pool too ...2-254, and statically set the devices. But i'm not keen on this DHCP set up. Also, it could be just me, but the R605 seems better controlled without being adopted by, and integrated, within the controller. But that could be just down to the layout. 

Also, the controller was not showing all wired clients, all the time, and it was very random. Some times I would see the wired devices, sometimes I wouldn't.

EDIT: 

So I decided to reset it and log into it before deploying it live. I was able to set a pool ...100-254, and I was able to set up static IPs outside this pool! Infact, I feel I could switch this with the current router and everything will just work. 

It does seem that you get the full functionality of the R605 in standalone mode. The only advantage of it being adopted by the OC200 is for ease of management. But you loose some functions.