Plex DVR with HDHomeRun

Have a few questions about running Plex DVR with an HDHomeRun Prime using a CableCard from TWC or Optimum:

• How many shows can be recorded at once?

• If I want to increase the number of recordings at once, can I add additional HDHomeRun units with additional cablecards?

• Can I record cable television shows using the HDHomeRun Prime with a CableCard?

Thank you!