#1
I was wondering how to make a super gritty sound that some heavier bands use a good example is Save The Castle Screw The Princess by Arsonists get all the girls
it happens around 1:40

i have also noticed the same sound in some of after the burial's songs
#2
I don't really understand, it just sounds like a normal palm mute in that song. But it you mean ATB's breakdowns from Forging a Future Self, they palm-muted a little further away from the bridge than normally. However, in Rareform, they have 8-strings. Which also gives them an intensely heavy sound.

Triplet palm muting (it has to be choppy )during breakdowns is also good for an extremely heavy sound in this context.

I don't really see how this is "advanced" though.
#3
well i was wondering if there was some like technique used to make the sound

Also when im talking about ATB i was thinking more of the end of steady decline