During the process of upgrade from SAV to SEP first the SAV client is uninstalled automatically and then new SEP is installed over it.
A SAV client cannot be managed by SEPM console as SAV and SEP use diffrent method and technology fo client commuincation.
also in SEP there is no concept of Parent server or Secondry or Primary server.
In SEPM only groups are present.
The clients report to the server on which the SEPM console is installed. This SEPM machine is used a server to the Clients.