Having lived through that era, the groups performed live, sometimes raising Ed's ire when they didn't perform the songs they were supposed to or did not modify the lyrics to "clean them up" for family audiences.
The sound usually was good, sometimes the artists sang to a recorded backing track but there was no lip syncing.
It was mono, of course and the micing was pretty simple.
An overhead, on a boom, over the drums.
Usually 635a's for the talent.
Amps were miced either on or off stage and again, the 635a seemed to be the mic of choice.
They were ubiquitous on '60's tv shows where bands were performing.
On some other shows, American Bandstand, for one, lip syncing was pretty much the rule.
Things were a lot simpler then.
And most of the talent could actually sing, unlike today's
"talent" who rely on autotune and multi tracking.