The card box holds up to 80 sleeved cards whilst the sleeves contains 65 matte-finish card sleeves in each pack
Functionally, Yuna's Whistle is a pseudo-cantrip that always replaces itself with a creature, and finding the creature gives you some +1/+1 counters too, so there's combat trick potential as well
Whenever you came to the game, whichever variant of a blue 1/1 that cant be blocked you prefer, they serve the same role: cheap bodies to exploit cards like Edric, Spymaster of Trest that reward you for dealing combat damage or a place to slap counters, equipment, auras, and whatever else you want to buff your army with
For example, if you attack with a 4/6 Wizard with trample and it's blocked by a 1/1 creature, you can assign 1 damage to the blocker and 3 damage to the defending player