I found a thread when searching called "Adding an OC200 to an already configured network in standalone" that is similar to my situation.

My network has an existing ER605 V2.0 gateway, SG3452P V3.20 switch, (1) EAP650 V1.20 and (2) EAP650 V1.26 AP's.  I tried to use the software controller after the fact but the devices fail to adopt as I probably need to factory reset the devices to be in the same subnet as the controller for adoption to succeed?  My software contoller install is not a smooth process with multiple windows open for Mongo database, Omada Launcher and then the Omada Controller and is slow to launch so I decided to purchase an OC200 to get a cleaner result.

I currently have only one LAN (VLAN 1) but plan to create additional VLANs after adoption for VoIP, Surveillance, IoT and WiFi.

As I understand it after the controller adopts the devices, their settings are deleted and then managed in the controller which is fine but I guess my question is this, is there a way to pre-configure the OC200 with a static IP in my existing 192.168.3.0/24 subnet and have it then find and adopt the existing devices or should I factory reset all the existing devices before connecting the OC200 and do a clean install?

I have backups of my configurations for all my devices in case I don't get it right or encounter problems and can revert back to a standalone setup if needed.

Thanks for any insight.