Absorption, Diffusion or a combination of it all?

OP. Anthony Grimaldi has an "acoustic recipe" based on thousands of rooms he has tuned. You may want to tweak it a bit but it gets you extremely pleasing results as a starting point. It starts at the :49 min mark in this video:

https://www.youtube.com/live/G0ekssXX7rE?feature=share

Both, is typically the answer.

Diffusion - and even deflection - has been the greatest help for my system, once the bass was tamed (with absorption).

According to the pro's pros, without a proper analysis of the room, you are guessing, and may make the acoustics worse.

I have experimented a lot over the years with acoustic panels, mostly from GIK. I have used both ears and REW measurements to accomplish what I like. I am currently all GIK. What worked for me best is:

Side walls: Combination of 242s and Alpha 4As

Ceiling: 242s

Front wall (behind the speakers): Alpha 4A and 6A

Bass traps: Alpha 6As (my corners are scaled, with multiple outings, so I can only “tuck them in” with overlapping Alpha 6As)

Back wall (behind my listening chair, about 10’ behind): Alpha 6As

I like the Alpha series a lot. Very versatile, as they are a combination of absorber, diffuser, and bass trap: https://www.gikacoustics.com/product-category/alpha-series/

All…thanks for your thoughts! 
I watched the video and it makes sense but isn’t easy to implement, no room is ideal as far as wall space, ceiling, windows, doors, etc. Good as a guideline though.

So since I’m already using the GIK 242 and 244 bass traps in the corners, I’m thinking to add a set of A2 Alpha Pro, exactly the same design pattern @thyname has in his room. Decent amount of absorption and enough diffusion. I don’t want to completely deaden the room. Still researching. Keep the thoughts and suggestions coming.