Violentmonkey
https://violentmonkey.github.io/
+
Bakugo's External Sounds Script
https://sleazyfork.org/en/scripts/31045-4chan-external-sounds
Auto-plays sound links in the image filename.
+
CSoft's Third Eye Script
https://git.coom.tech/cunnysoft/third-eye/src/branch/%e3%81%aa%e3%81%84%e3%81%9a%e3%82%8a/third-eye.user.js
Auto-replaces the images with the booru link if it's a booru filename, hence you can post one image, while linking a completely different one. It's not a full-embed, but it's the next best thing while staying in the rules.

and that's all you really need to see the secrets that standard users don't.

HamletDuFromage 4chan Mass Reply if you want a fuller (but ultimately optional) shitposting suite.
https://github.com/HamletDuFromage/4chan-mass-reply

For sounds, use https://meyerweb.com/eric/tools/dencoder/ forthe filename. Filename will look like
(Filename)[sound=https%3A... .mp3].png / .jpg / .gif / .webm etc