Yes, they are exactly the same. Simple and emphatic denial depend on how you stress the words in each sentence. It doesn't depend on the two sentences themselves.

Yes, the meaning is the roughly the same, but depending on the context, the latter one has more emphasis to it. For example: Did you kiss my daughter? I would never do it. [a simple denial] Did you kiss my daughter? I wouldn't ever do it.(!) [an emphatic denial]

"I would never do it" would be the more proper form of English. The 2nd form is more like instead of saying, "I didn't do anything" vs "I didn't do nothing". The second form is lower class English, spoken by the uneducated.