That guillotine choke is the first one I learned and the first one I teach. I find that the more wiry a person is, the easier they pick it up and eventually become proficient with it. I love that choke.
The t-shirt choke - I prefer a different collar choke from the bottom. I was never told a name for it and was never able to find it on youtube (probably because I don't know the name) Maybe I can explain it.
From guard - pull them with your legs so they post, wrapping your left arm around their right arm to control it. Your left hand goes to their left collar (near their neck area) your hand is palm towards you, knuckles toward them. With your right hand you reach past your grip on their collar (by the back of their neck) In self defense we usually do this by slapping upside of the head, then grabbing the back collar.
Now you loop your right arm over their head - if the opportunity is there. Otherwise, you push your forearm against the side of their head/neck (their left side) like you're trying to bend their neck to their right - then give them "an out" so you can loop your arm over.
You know what comes from there.
Why I prefer it is because it works against any kind of clothing. The one shown in the video is great against t-shirts and the like, but not against long coats, winter coats and thick leather jackets. (I live in New England) We've worked it against any and every kind of clothing. Suits, tuxes, raincoat, leathers, dress shirts, big winter parkers. The only thing it sometimes doesn't work with is if someone has an old t-shirt with the t-shirt collar torn off (Think New York Italian, circa 1980's) sometimes the shirt just rips - in which case you go to something else. Including the fashion police.
I know a decent Jits guy can counter. But I've pulled it off a few times against blue belts in class.