Yes you can join as moderator from a telephone connection. You need to just ensure you connect meeting using a moderator pin. You get option to mute and umute audio connections of participants. * 8 command can be used to mute all and unmute all. Participants connecting over phone connection can mute/unmute there connection using *4 command.
Moderator can use "Auto-recording" feature to record a audio-only meeting.
Please find more information regarding audio-only meeting in below knowledge base links: