Depends on which techniques. Grappling someone who outweighs you is always a dangerous proposal--if the skill gap isn't big enough, you get smushed. And there's a level of skill that a bigger opponent can have that just prevents you from effectively catching up. Heel hooks have been called "the great equalizer" since they tend to work despite massive size disparities, but a lot of other techniques can theoretically be muscled out of if someone is that much bigger and stronger, and has at least some small idea of what they're doing. As for the techniques in this video, they're... honestly not all that bad, I expected worse. I can see using variants of these in BJJ now and again. Some are over-the-top, or require too much to go "just so", and some are less effective than moves that are already common. But a lot of sound mechanics. The scenarios are unlikely though, even in more "self-defense, foh da streetz" stuff. People tend not too go after you with a two-handed rape choke--but they might grab your collar/lapel, and then a few of these moves should still work. I've never heard of someone trying to strangle someone from behind with their hands like that, but it's pretty common to see someone try a standing rear-naked choke, in which case some of these might work if you catch their wrists early enough. Pressure test with a partner and see what you get. That's what I'm looking to do.

The answer is that it "can". I use the word "can" instead of "will" or "would" because it depends on the skill of both people and their physical condition.

Use it or dont

Sometimes, and depending on the size difference. Even a big rock off balanced will fall.

Martial arts is all about adaptation of principles to a situation, if you don't understand principles behind techniques don't blame it on the art