Leinore grants +1/+1 counters and has zero power herself, allowing Coven to be triggered with ease
In short Learn lets you draw an optimal card and cards with the keyword often give you some other effect on top of it
If the creature token is a copy of a creature, then it has the mana cost (and thus mana value) as the original creature, so the token deals damage equal to its mana value like the original creature
Since there are only a handful of conspire cards, you can use Rassilon, the War President or Wort, the Raidmother to give conspire to your other cards, which you can use to build a whole deck around
Theres no objective, quantifiable way to measure juiciness or x-factor, and part of the beauty of Magic is how different players will have totally different takes on a card depending on which decks and formats they prefer