Well, if i understand it all correctly, BepInEx can inject plugins by itself, in the folder <Koikatu/BepInEx> , and even run IPA plugins, which you download with the structure <Koikatu/BepInEx/IPA>.
BepInEx can also run ZIP mods, that must be installed in the folder <Koikatu/mods>.
Everytime you download a plugin (.dll), put it in BepInEx. If it comes in a IPA folder, it is BepInEx/IPA, and mods that comes as .zip and have a manifest.xml must go in the mods folder, but not extracted, only the .zip file.
I do not use the HF patch myself, since things get updated and sometimes, the patch don't follow...
The Lewd-H Koikatu pastebin (as un0wned already posted) have the links for the lastest BepInEx and its plugins too. Now, 3.2 and v4, respectively.
I would recommend checking it regularly and not relying only in a all-in-one patch.
(i don't know which uncensor comes with HF patch but there are more than one and they are quite different, for example)
ps: still i praise the work the people from HF did and still do, it is just that patches tends to become outdated pretty often.