Best approach to merge 2 F5 configs ?

Yes, right. The certificate and key are the default cert and key. They are not required for the transaction.

 

From this perspective it should be fine to merge the modified configuration file as described above.

 

Make sure to use the same VLAN names as they may be associated with your virtual servers.

 

Remove the floating self IPs and routes and some other information which already exists or is in conflict with the configuration of the target system.

 

And create a ucs archive of your target system before running all kind of changes, please.