when installing TMSWebCore for Lazarus and Delphi 10.3 on the same computer (WIndows 10) which TMSWebServer should be registered? Is there any difference between the delphi and the Lazarus version. What would be the commandline to register the TMSWebServer without using the installer?

Best regards

Lazarus should be able to use the one that is registered with Delphi.
In the Lazarus settings, point the debug web server to the Delphi instance.