Just some notes because I basically had nothing to work off of when building this.

There's a lot of different cards you can run in the flex spots. I liked reasoning because it felt like you had a chance when going 2nd due to your monster levels largely being unknown to your opponent, but I also ran different pots, handtraps, and spells. I tried trade-in, and it wasn't very good for me. Wing Requital was a much better card. I experimented with Anti-Spell Fragrance and it was also decent.

Main deck Wynn is only okay and can be replaced, since she locks you into wind effects, Alector was also used in that spot. You can run some level 5 and 6 Winged Beasts to work with the Simorgh spells, secondary effect. Cheating them out with normal summons is decent but frankly there aren't many good targets.

I tried a 60 card grass variant with Lyrisics that was also okay. It gives more options for Sovereignty to pull but reduces your turn 1 consistency which is all this deck has.

Most of the ED is flexible which sounds nice but in reality its because there just aren't many good cards. Greatfly was not good but Fire Fighting Daruma Doll was decent and definitely playable. I think I summoned the level 7 XYZ I was running one time, so I just cut it. Its very rare to want to give up your Apex Avian (you can also run 2 if you want).

Things I didn't try: Harpies, Icarus Attack, Lightning Chidori, anything related to Monarchs, Totem Bird, Silpheed

Overall this deck is okay but it feels like a Floowandereeze/ Bird of Perfection waiting room in some ways.

What exactly would you consider core to the main deck? Interested in building around the flex spots, but not sure exactly what's necessary for basic functionality.