Which is correct?
He lives as he wants
He lives how he wants
They are both grammatical and they both mean essentially the same thing.
He lives as he wants.
He lives how he wants.
→ He lives (in the way / in the manner) he wants.
In the first sentence, as is used in the following sense:
: in the way or manner that
// Do as I do.
The statement is fine grammatically. The social or target audience may see it differently. As presented, it's vague.