Hey folks, so I finally received my frame after waiting since February. 120mm rear end. Can someone confirm for me that the hardware I need to mount my 2023 Rockshox Deluxe Ultimate is 30x8?

Seems like a conundrum to me.  Have you asked if you can purchase a primered frame?
If not;
Ask if they are powder coating their frames. 
Then find out if they use a water base paint, or solvent based paint. (Can make a difference in what paint you use and your preparation.)
If the frame is clear coated over their color paint, then at a minimum, the clear coat will have to be sanded, and perhaps sealed, before you paint the top coat you want.
If you receive a bare frame, then you will likely have to fill and sand any defects on the frame, before the primer, color layer, and perhaps clear coat.
(The other thing I don't like is that if you paint over their paint, you are adding more weight to the frame.  Not much, but it adds up.)

On a side note, Automotive/high quality paints have become so expensive here in the states, ($50+/qt) that I would consider paying the price that the frame seller charges to custom paint your frame.  May be worth it in the long run.

You're right in that it would make the most sense to have Carbonda do it from a paint quality perspective. However the person I am asking to do it is a pretty accomplished artist that has also started making his own steel frames (and painting them) so while the paint job won't be as durable, I know he will do something cool and interesting and that ultimately matters more to me than the quality of the products being used. And yes, it will also cost more.

This is what Wing sent me initially for paint options:

standard matte : free
standard matte is between black matte and UD matte , It have clear coat protect the paint
 
UD matte , UD glossy : $105
One color: US:$70.00(matte or glossy,solid color )
Two colors: US$ :95.00 ( all matte or all glossy,solid color )
Two colors: US$ :105.00 ( matte and glossy,solid color )
Two color gradient : US$ :115.00 ( all matte or all glossy ,solid color )

I asked him for more information about what standard matte is. I'm hoping that someone here might be able to shine more light on this too. My friend meanwhile said that standard matte should work since he will have to do sanding prep-work regardless.