This is similar to how it's typeset in TeX as well: two for en, three for em.

I have used two hyphens, but I appreciated text editors collapsed them into an (em-) dash.

Hyphens are simply for connected-words while dashes are -- for better of worse -- to make asides.

> Personally, I think two hyphens also looks better than just one

It's context-dependent. (Aside: you wouldn't write "context--dependent", which is the use case of the hyphen.)

Ostensibly the en dash is primarily used for ranges, although that's a case where I'm inconsistent. I won't typically write "A - Z" or the technically correct "A–Z", as I think in that case I tend to write "A-Z", using a simple hyphen. I certainly won't write "A -- Z".

The em dash is even wider—it's not typically mistaken for a hyphen.

Sometimes I write A->Z.