Saheeli, the Sun's Brilliance

The token copies exactly what was printed on the original permanent, with the listed exceptions (unless that permanent is copying something else or is a token; see below). It doesn't copy whether that permanent is tapped or untapped, whether it has any counters on it or any Auras or Equipment attached to it, or any non-copy effects that have changed its types, color, power and toughness, and so on.

If the copied permanent has in its mana cost, X is 0.

If the copied permanent is a token, the new token that's created copies the original characteristics of that token as stated by the effect that created the token (with the listed exceptions).

If the copied permanent is copying something else, then the token enters the battlefield as whatever that permanent copied (with the listed exceptions).

Any enters-the-battlefield abilities of the copied permanent will trigger when the token enters the battlefield. Any "as [this permanent] enters the battlefield" or "[this permanent] enters the battlefield with" abilities of the target permanent will also work.