The video you posted showed alot of techniques that could be used in an MT fight. Head side underhook with a far side overhook, Shoulder bumping for space and throwing punches, head control with the collar tie. He probably learned most of that from Catching Wrestling, but they are universal grappling concepts no matter where you learn them. As for him being the inferior striker, Barnett was the better infighter, and moved straight to were he was best. There's generaly outside, the pocket, and inside. A fundamental concept of fighting is to move the fight to the range or postion you have the advantage. Outside, inside, against the cage, takedown to side control, pull guard. Its fighting 101.
The same way you talk about being footsweept from the "Thai Plum". If i grab a double collar tie and you posture up, you are going to lift my base and then you could well sweep me. If i have my elbows pivoting on your collarbone and pinched together tight, i need to breakdown your chin to your chest, then get your head to below mine. At that stage i control your head and posture. A universal concept of grappling is that if i control your head i control your balance. Your hip should be back and your spine bent over and weak. If you attempt to sweep or shoot, i use my elbows as a frame and drive your head down or swing you. I can now knee, release a collar tie to elbow/punch, or snap down to a front headlock.
You talk of these this positions like they are static, and doing X results in Y. There are counter to everything, there are counters to those counter and so on. If i stay anywhere too long and don't defend the counter im going to end up at a disadvantage.
There is strenght in questiong what you "know" to be right. Thats how you get better