The basic introduction is already covered in the video, here provide a detailed explanation about the installation and configuration of the plugins.
KK_TransparentBackground.dll
This is the most important plugin for desktop dance, but seems it is not included in HF-patch. Get it from https://blog.maki0419.com/2020/05/koikatu-transparent-background.html
Download link at the buttom of page. And you have to assign a shortcut key for it to enable.
If the transparent background doesn't work, check the following 2 points:
1. Disable MFAA and FXAA in your graphic adpator setting (e.g. in NVIDIA Control panel)
2. Disable the depth of field in studio scene setting (as following picture)
BTW, because this plugin only has KK version, we cannot do the same thing in HS2, sadly.
GraphicsSettings.dll
Included in HF-patch, or can be found here: https://github.com/BepInEx/BepInEx.GraphicsSettings
When dance on tesktop KK runs in background, so you have to enable "Run in background" and DISABLE "Optimize in backgound" (optimize here means stop anti-aliasing). Other options are not related.

BepInEx.EnableResize.dll
Included in HF-Patch, or can be found here: https://github.com/BepInEx/BepInEx.Utility
A plugin very easy to understand, just remember to restart studio.

HideAllUI.Koikatu.dll
Very well-used plugin, included in HF-Patch of course! or can be found here: https://github.com/BepInEx/BepInEx.Utility
No need to config it, default setting is OK.
Configration of MMDD is introduced in video, but some points here:
1. You can load mutli character for multi character dance. However, it is not recommended to copy dance as it takes up too much screen space.
2. Hide the MMDD UI after started dance, or the "Next dance" shortcut cannot work. It is a bug of MMDD v2.9.4, and thats why I set the "GUI on Playing" to normal.
3. Try put your favorite characters into a folder and set it in Playlist->Dancer to enjoy.

The scripted scene demonstrated at the end of the video is for my patreons:
https://www.patreon.com/posts/kk-scenedata-v1-101831290