The X you pay won't affect the token, but will deal that much damage to any target you want
Even if you're only looking at Commander, this allows you to put a Sol Ring directly into play, but that's probably the tamest thing you can do with this thing
Perhaps the most notable exception is Harmonics Messiah, a being of incredible power which converted a chunk of the invading Link Joker clan into non-hostile inhabitants of the planet Cray and is treated in near-deific terms by the lore, yet in game is a promo Stride with no effect
Closet ruling I could find, it implies it remembers being Special Summoned, so if it does that, that probably means it would know it was Normal Summoned from your hand or Special Summoned from your GY etc.
We dont have a lot of information on which Legends will appear here, but it is know that both Ragavan, Nimble Pilferer and Atraxa, Praetors Voice will be making an appearance