Depending on the runtime, the configuration file is located in the following place: see Location of the configuration file

Define the port

[CmpOPCUAServer]
NetworkPort=4841

Binding to an adapter

[CmpOPCUAServer]
NetworkAdapter=eth0

Max. nodes per read (>=SP17)

[CmpOPCUAServer]
MaxNodesPerRead=100

Max. Sessions (>=SP17)

[CmpOPCUAServer]
SessionsMax=100

Max. Speed

[CmpOPCUAServer]
ItemMinSamplingRate=100 ; ms

Deactivating

[CmpOPCUAServer]
SECURITY.Activation=DEACTIVATED

Restricting Mode or Policy

[CmpOPCUAServer] 
Security.CommunicationPolicy=POLICY_AES128SHA256RSAOAEP ; can be POLICY_AES256SHA256RSAPSS, POLICY_BASIC256SHA256, POLICY_BASIC256, POLICY_BASIC128RSA15
Security.CommunicationMode=ALL ; can be SIGNED_AND_ENCRYPTED, MIN_SIGNED, ALL,ONLY_PLAINTEXT

Namespace change for OPC UA server (>=SP17Patch2)

[CmpOPCUAProviderIecVarAccess]
UseNodeName=1
UseNodeNameForNodeIds=1

or 

[CmpOPCUAProviderIecVarAccess]
CustomNodeName=MyPLC123

This will let you use the nodename instead of the device name.  You then just have to fix the devicename.
You then do this by changing it via the IDE (see OLH: Device - Rename Active Device), or with either of these config file settings.

[SysTarget]
NodeName="TEST"
NodeNameUnicode="T\00E\00S\00T\00"