Interesting, I had no idea.
So I've downloaded the Forge 1.12.2 installer, and the mod. What do I have to do with Twitch now? I found and downloaded the TwitchSetup thing and I see the Minecraft option in the Twitch settings, but I'm unsure what to do next.
Edit: The video you attached didnt show for me but I see it now, oops
I have Forge 1.12.2-14.23.5.2844 downloaded and installed as a profile. I downloaded the zip file for DDSH V. 5.7b and extracted it into the mods folder in .minecraft. When I run minecraft, only the four default mods come up. Not sure what to do, tried looking up on google, no luck.