If the spell that's copied has an X whose value was determined as it was cast, the copy has the same value of X.

The copy is created on the stack, so it's not "cast." Creating the copy won't cause abilities that trigger when a player casts a spell to trigger.

The copy will have the same targets as the spell it's copying unless you choose new ones. You may change any number of the targets, including all of them or none of them. If the spell is a permanent spell with targets, such as an Aura, you may also choose a new target for that spell. The new targets must be legal. If, for any target, you can't choose a new legal target, then it remains unchanged (even if the current target is illegal).

Spells that were cast before Storm of Saruman count. If Storm of Saruman was the first spell you cast this turn, the next spell you cast this turn is your second spell.

If the spell has damage divided as it was put onto the stack, the division can't be changed, although the targets receiving that damage still can. The same is true of spells that distribute counters.

If the spell that's copied is modal (that is, it says "Choose one —" or the like), the copy will have the same mode or modes. You can't choose different ones.

If a permanent spell is copied, it's put onto the battlefield as a token as the spell resolves rather than putting the copy of the spell onto the battlefield. The rules that apply to a permanent spell becoming a permanent apply to a copy of a spell becoming a token.

You can't choose to pay any additional costs for a copied spell. However, effects based on any additional costs that were paid for the original spell are copied as though those same costs were paid for the copy too.

Any choices made when the spell resolves won't have been made yet when it's copied. Any such choices will be made separately when the copy resolves.

The token that a resolving copy of a permanent spell becomes isn't said to have been "created" and won't interact with abilities that care about tokens being created, such as that of Rosie Cotton of South Lane.