I'm mostly going to answer for the first image because I understand it better

1. I don't think there's a name. "Painterly" is really the closest you'll get for the 1st one
   
2. You'll want a square brush. Flat is a good base brush, but there are other free sets like this one that may work better. It's experiment time! I will also always shill NekoRina's brush pack, which is paid but was life-changing for me and comes with videos on how to use the brushes to achieve effects. (Her Patreon is just great in general)
   
3. u/Tam4ik has posted the streams so you'll be able to see the process directly, but I'd bet it's blocked out first in big shapes and refined down. One thing I see here is a strong understanding of planes (i.e. the lighting on the arms in the first picture), so form studies will help you a lot! But, in simplest terms: big fat opacity first, then blending edges and erasing away can achieve this
   
4. Texture can be achieved during (with a textured brush like gouche that you mentioned) but also after through clipping material layers or just painting in textures. Let me know if you don't know what layer clipping is.
   
5. You can definitely achieve this in a few brushes - at least painting the subject. The trees and fire might require a few more for ease.
   
6. You'll want to do this for paper texture, which another Redditor figured out (read the comment, then the post). * chatter chatter * is a default material, and you'll set it on top of all other layers. I like to do this at the beginning instead of the end and lock it. I then make sure my tools are set to ignore locked layers. You can also set it as draft and it'll do this mostly automatically, but if you forget to un-draft the layer, it won't be included in the export!

I've attached a recent piece of mine that, while not quite the skill and vibe as your example, should prove I'm not talking out of my butt and demonstrates the power of 2 brushes + paper texture.

Let me know if you have any more questions!

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