To me, avid - like an avid gun collector. Devout implies reverence, as in devout Christian. That seems less intense, quieter to me. Besides, avid sounds like rabid.
Excellent. Pretty much what I would have said. I’m in the avid pro-second amendment group. I’m not a collector but I own a handful and I’m a strong supporter of gun rights. That’s avid and intense. Like you said, I consider devout like a devout Christian, Muslim, or mother.
Depends on the context. Most devout feeling probably sits in the background of a person's life, informing and directing everything they do. But in the second meaning of devout, total commitment implies something perceived as possibly lasting for life.
Avid comes closer to the second meaning of devout in terms of commitment and intensity, even reaching as far as fanaticism - and yet for me, despite "commitment", I can imagine avid being used to describe a transient feeling. Someone could be an avid sports fan, and yet later grow bored with it.
I don't think I could generalize either way, because I think it depends how the words are used in context.
~ devout
dɪˈvaʊt/
adjective
having or showing deep religious feeling or commitment.
Avid -- having an extreme desire or enthusiasm for
People are often willing to die because of their sincere and heartfelt beliefs and convictions. That is more intense, to me, than any desire for a thing or any activity possibly could be.