There's a fine line between the 2. I've shot some factory guns that are way overgassed, like Ruger AR's. They do that so the rifle functions reliably. Some people don't even know their rifles are "over gassed"...
Yes, the line is fine, & the only real way you can get to the optimum gassing level is with the use of an adjustable GB, which the OP has said that he does not want to use.
W/o an AGB, all else is some level of a compromise & one should always, always err to the side of reliability, which by default means to the bias of being (to some level) overgassed.
End of story, all else is fantasy & BS.
And while different muzzle devices affect muzzle jump & apparent perceived recoil, they do not affect the spring or buffer being used.
MM
