Based on Japanese community opening data: 23 SR cards per box (guaranteed), roughly 1 SEC per box, 1 Leader Parallel per 6 boxes, 1 SP per 12 boxes (1 per case), and 1 Manga Rare per 72+ boxes (1 per 6 cases)
Nihilego can do the same, and its especially effective against the popular Reshiram & Charizard- GX
The reprint value is pretty impressive in this deck
28 see the below trailer, which confirms the date but now the day is here, theres no sign of the feature going live
Each mini-pack also has 3 standard Gold Rares 1 card never released as a Gold Rare before, plus 2 of the greatest hits from a past Gold Series set
By the end of the series, Yuya has access to all of the dragons that represented the various dueling dimensions he encounters, fortifying his deck with these dragons that can dominate the field