If I interpret your post correctly, and there's some doubt about that... I think you're saying, you installed a muzzle brake and the resulting report/concussion was more stout than you expected? Especially being close to the muzzle/without using a pistol brace?
Is that it? If so, can you post a pix of said brake. Or is it the KT OEM unit?
Yes, muzzle brakes reduce recoil and increase noise and blast. They always have.
In a 9" barrel you have everything working against you. The powder burns in maybe 10-12" of barrel and the PLR-16 has a 9" barrel so just as the pressure is peaking the barrel comes uncorked. So yeah, deflecting that blast out to the sides (I assume) will deliver a thump to you. You want to really experience something try it without hearing protection if you want to know what pain is.
Interested to know how it works with the arm brace and the linear comp'. But I think it's still going to be intense. That's just the nature of uncorking 55k psi.