What is the difference between mono, dual mono, and stereo when recording and after the recording process?

Answer 1

Mono is one audio signal.

Dual mono is the same audio signal duplicated in both Left and Right channels.

Stereo is two different unique audio signals in the Left and Right.

It really depends on what you're trying to record. Generally, you record your instruments (guitar, vocals, etc.) in mono and have your final songs in stereo. But this is the very simplified answer to what sounds like a more nuanced question.