The R18 patch is also in the wild and linked several times in this thread: here - https://f95zone.to/threads/custom-order-maid-3d2-its-a-night-magic-final-kiss.34314/post-2221585
No you add the H-patch to the base game, you'd need both for the full experience. And yes, the H-patch is larger than the base game itself.
I was asking where the patch was but but I found it here https://f95zone.to/threads/custom-order-maid-3d2-english-ver.34196/page-3#post-2216329 which is what you linked earlier
Go to the 'Maid Admin', pick the 'Unique' maid, and 'Edit' her. Bottom left of the screen is a 'Pre.Save" button. Save her Clothes and Body combined preset (left button). Exit the editor. Now use the option to 'Hire' a new maid, and apply the preset.
Actually it's pretty easy to remake them, you can edit the maids and save them(I've edited every extra maid to have better skin) which allows you to save her as a preset. But otherwise extra maid personalities are just future dlc teasing you.
To install dlc there should be something called an update.exe in the dlc you run that and point it towards the main game, if there isn't then I'm not sure you grabbed the dlc. Apparently linking the Japanese CM3D2 to the English COM3D2 isn't possible right now. They translated the opening which would only play if you had the Jap copy though, so maybe they plan to add it in the future.
