So, for low poly you won't need anything fancy. Blender for the modelling and texturing, although you could always export the UV grid and paint it somewhere else, once you're done with it you export it to Unity and then you turn it into a VRM, after that you can use any VRM software but I recommend VseeFace.
This pal made a good video on it
https://www.youtube.com/watch?v=i2pOourRdFUAlso his low poly model looks great, so you might want to use him as some sort of reference instead of something like YIIK or god knows what. Low poly aesthetic is relative, you don't need to make a model that would run in a PS1 game, just make something that looks like it would.
But all of that is for once you already got a set and ready model with textures and all, but you've yet to make a model, so let's start there.
You'll want a reference sheet, and also possibly a model that you like, at least to know what the fuck you're supposed to be doing. You can not use the model, but I recommend having it so you have some sort of idea of what you're supposed to do.
Ok, create a cube, create an edge loop right at the middle, delete the vertices on one side and then apply a mirror modifier, this is normal for a lot of models and you'll se it done in almost every symmetrical model. The body should be simple, just create something that looks similar enough to your chuuba's character sheet, after that create some edge loops so to create arms and legs, and then extrude them until the length seems alright. Detail and model so it resembles your chuuba, then again use reference to have an idea of what you should be doing when you encounter something that you don't know how to deal with, which at this stage is probably everything.
Once you have the body ready, move onto the head. Make it simple, don't get whacky with bezier curves for the hair or the likes, you're making a low poly model. The eyebrows can be a simple floating plane and the mouth doesn't need crazy anime details. Again, that guy I linked has a good model, you can see how his model looks in edit mode in the shape keys part of the video and get an idea.
After that, you must UV unwrap, for this you must make a lot of seams so to make the texturing easier. The texturing itself should be easy in a simple model like this, be sure to not go crazy.
A couple of tips, if your chuuba has a lot of crazy stuff like ribbons and the like, you can simply make a plane and then use textures with transparency to make the desired object. Make sure to use alpha when you make the textures. Also select alpha clip in the material you are using so the material actually looks transparent in the parts you want it to.
Once you have that stuff ready follow the video above, it's well done and should apply.
This is not a super detailed guide, search as much as you can for the starting process of making a model, a low poly character is easy.
