No additional options?

Any equip you use it on acts like it's a Superior equip based on level. Root Abyss stuff would gain the same stats as Tyrant equips, unless it's a weapon, then it gains the normal attack bonus from enhancements and then all the stats it would if it were superior and an extra attack per star 6 and above. Except unlike superior equips, you can use normal shielding wards and go up to 12 stars, and the chance of passing stars 10 and above is higher than with AEEs.

what are the rate for MEE scrolling?

1 star = 60%
2 star =?
and so on?

12+ star? = ?