Everyone has a dark side to them, even if they won't admit it. We all have things about ourselves that make us uncomfortable.
FYI, YG discusses having OCD and depression in his song, The Last. In the music video for the title track, Agust D, he's in a messy, chaotic trailer and has been tied to a chair. I think was supposed to represent two things: YG's mind where he keeps the alter-ego, Agust D, locked away in the messiest part of his mind where the symptoms of OCD and depression are born. I think it also represents his breaking free in the music industry and breaking free as a person. When the alter-ego frees himself from the chair, then gets out of the trailer altogether, he is getting out of the messy zone in YG's mind, he's exploring the music industry, and he's also still holding onto the trailer because it is a part of him. It's like an acceptance of the things he can't completely change, but can at least bring balance to.
YG brings back the alter-ego in the music video for Daechwita, where two sides of him are fighting over territory. The bad side, the "king", has really caused some serious problems and the other side, who is not the friendliest character either, executes the bad side in the end. It's an unsettling video because YG is doing away with an unwanted part of himself, but it's also empowering because he's taking a step forward and making a hard decision for himself to do better and live better. I think the pandemic really made him stop and take a look at himself, emotionally and physically, and explore things he'd never been interested in before. Pre-pandemic, YG didn't do much of anything. Post-pandemic, he's shown interest in being more social, taking up artistic/creative hobbies unrelated to music, started working out more, and in general seems to be a healthier person.
YG is not quiet, lol, this is known. It's been known since this dude hit the spotlight. As far as calm is concerned, he truly is a very even-tempered person. He has his random, hyper moments, but those are usually driven by the presence of others.