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.

You can't choose to pay any additional costs for the copy. 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.

As a copy of a permanent spell resolves, it's put onto the battlefield as a token rather than putting a 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.

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. The new targets must be legal.

The token that a resolving copy of a permanent spell becomes isn't "created". Abilities that refer to a token being created won't interact with the copy resolving.

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

The triggered ability and the copy it creates will resolve before the spell that caused it to trigger. They resolve even if that spell is countered.