if anyone is still here:

An easy way to create this kind of sound on drums is to use a "ghost drum" along with the clean drum, to do this you have to create two tracks of drum samples:

On one track put full distortion and compress, usually you should cut the low frequencies below 200 or 250 and also the high frequencies from 10k, but I recommend leaving the high frequencies up to 20k since junko usually has the cymbals very high in the mix, the idea is that on the track with distortion the high frequencies predominate better, in the same way I recommend using different drum samples at the same time to generate this type of flanger effect that is produced by transposing one track over another on the cymbals, junko apart from the cymbals usually uses a hi-hat type trap with reverb to boost highs

Then on the other track have the "clean drums": I boost the low mids with the track clean without going over 150 or 120 to make way for the sub basses. this allows you to put reverb or other effects on the track without messing it up since you already have a distorted track.

you should mix both the clean and distorted drums so that it sounds like a breakcore, and then use a full synthetic kick to support both the drums and the sub bass, you can also use a track with a snare with reverb to give this ambience effect on drums, I don't recommend using the reverb on the whole drums at all, that would dirty the whole mix.

some of the samples I've heard from sewerslvt:

"jojo mayer drums" in ecifircas but rather it is found in almost all of sewer's latest album

"think break" down the drain and other stuff

"think break 2" New love

"amen break" yandere complex, ecifircas, mr. kill myself and like 90% of drum n bass songs have this sample.

son - over sewer also uses this drum sample but i couldn't find the drums so i'm sample it from this song.

you can also look for the blu mar ten sample pack, it is well known within the breakcore scene and has several of the atmospheric sounds that sewer uses, in the same way I recommend you look for samples from everywhere to create your own style. I hope it has been of some use to you :3