SuperStar Level Caps are tied to Rarity:
Ultra Rare level cap 60
Very Rare level cap 50
Rare level cap 40
Uncommon level cap 30
Common level cap 20
Default starters level cap 10
SuperStars unlock their 2nd skill at level 20
After unlocking their 2nd skill, SuperStars unlock extra skills every 10 levels
SuperStars gain energy every level
Higher quality SuperStars have higher stats