Will a work plan or job schedule be sent to a client, and can this plan be processed without a JobScheduler server being available?
JobScheduler itself does have a work plan or job schedule - it is not necessary. Similarly, we do not differentiate between server and client JobSchedulers.
Every JobScheduler works with its own configuration (which it can receive remotely from another JobScheduler) and is thereby independent of other JobSchedulers. At the same time, each JobScheduler is able to control processes on other JobSchedulers (remote execution) or on Job Schedulers on other servers (SSH execution). In this manner, each JobScheduler installation can be seen as operating as a server and/or as a client.
JobScheduler Agents, however, are exceptions: they do not have their own configuration and their jobs are controlled remotely by another JobScheduler. This arrangement comes closest to the classical client/server architecture.
The robustness of JobScheduler against failure can be ensured by the installation of one or more backup JobSchedulers.