Hi, I'm running GIK absorbers and bass traps on front wall, the sound suffers a little without them. Considering moving to something like Acustica Applicata Daads or Stillpoints Apertures which offer a combination of diffusion and absorption.
On the front wall I prefer absorption panels with some kind of limiting reflecting front plate. The Alpha panels from GIK are very good for the price. I much prefer Apertures though. Apertures, although silly money, sound the best to me on the front wall and all reflection points. I have tried a bunch including pure absorption, pure diffusion and various mixes.
There is no right or wrong, experimentation is the only way. Buy a few panels of a different type and give them a try.
Advanced, how do you set up your Apertures?
Tima has been running his room with vertical columns of two panels on the front wall: central and maybe 3' to the R and L, so six Apertures in total on front wall; and at side wall first reflection points.
For me, I use the panels to cover windows but they are symmetrical. LR about 24” away from center. So no experimentation. I would say because of those windows, treatments at the front of the room are more important for me than they might be for someone with a solid wall.