One thing I forgot to specify for the Extra Smooth one is that
please place the Pivot Point of the Lips at the middle of the "line."
(When the lips are in a straight line form, put the Pivot Point at the centre.)

✦ App: Alight Motion

All Mouth Tutorials:    •  Mouth / Lip Sync Tutorials  
Vector Drawing Tutorial:    • [FREE] How to Animate Using Vector Dr...  

✦ Citations:
All the Channels of the people I collaborated with and the tutorials can be found in this playlist.
(   •  Mouth / Lip Sync Tutorials  )

Yiko:    / @yikokocrunch  
miraclé:    / @ediyum  

[There are subtitles in 37 Languages.]

✦ Chapters:
00:00 Intro
00:17 CHOPPY (basic + tools)
02:40 SMOOTH & BOUNCY
05:33 EXTRA SMOOTH: Setup
09:30 EXTRA SMOOTH: Vampire Teeth
09:42 EXTRA SMOOTH: Setup
10:23 Saving the Mouth as an Element
10:47 EXTRA SMOOTH: Animation
15:18 Mouth Turn is possible.
15:37 How to Attach the Mouth to the Head
16:18 Credits

✦ Alternate Titles:
How to Angle the Mouth
How to animate Vampire Teeth
How to attach the mouth to the head
How to animate mouth gacha
mouth free
BEGINNER FRIENDLY

✦ Keywords: (testing)
gacha
mouth
mouth tutorial
lipsync tutorial
gacha lipsync tutorial
gacha alight motion tutorial
smooth lipsync animation
gacha tutorial