I did not consider diabellstar as a duality target, but that does sound pretty cool

Grass is just personal preference, for witchcrafter patronus it's the best recursion witchcrafter has and is something you would want on a turn 1 endboard. the shaddoll is just for winda floodgate via nadir servant

Duality Granguinol or Verre into Vice-madame, or a discard fodder for witchcrafters. Essentially acts as an extender when you don't draw either branded cards or witchcrafter cards. If dragoon gets unbanned, summoning dragoon becomes an option too, although I don't really know how much that would be viable for this deck.

Thank you for requesting! though I don't think I'm not qualified enough to make a guide of this, so I'll just write the rundown in the comments here.

The general combo is (1) sending schmietta to fusion summon Vice-Madame, (2) use schmietta to send patronus, (3) chain vice-master on schmietta to summon edel, (4) use edel effect to summon other spellcsater monster in the GY (another witchcrafter or cartesia, preferably), (5) chain vice-master to add patronus from GY to hand. You end with Vice-master and Patronus, with either a witchcrafter monster or cartesia for your opponent's turn.

The branded and shadoll cards are tech to play through handtraps and provide minimal disruptions when you can't summon vice-master.