Okay, I decided I needed a 1K texture, per square meter, of the game, but getting that on curved surfaces was really difficult, made some standards, some flat planes with reference textures on it, then put a 2K version, of the reference, on the unwrapped character, to make sure each surface of my character has the same ’ pixels per face / surface area ’ in the game, so it looks consistent, the pixel concentration, across all the models, it’s a bit complicated, but it looks nice and, feels good, solid . . .
Also, made two materials, and unwrapped the model, and made the head have a 2K per square meter pixel concentration, so the head is more detailed, has more pixels, but is one mesh, so the ’ squares ’ are closer on the face, because there are a 2K texture per square meter on the head, and a 1K texture per square meter pixel concentration, on the body, to get a more detailed head, it’s a bit complicated, but it means I control it such a way, that EVERY 3D mesh in the game, has a standard pixels concentration, per square meter surface, 1K for ground textures, 2K for heads, 1K for most models, even bend or, oddly shaped 3D models, like curved stuff, characters, all sorts of stuff, has a standardized number of pixels, per surface, as can be verified with eye measurements and, approximations, visually . . .
The principle is, the reference sheet has a 1000x1000 pixel texture, with a reference - standard on it, so I know that one box, equals 5 pixels, or 0.5 cm . . 1000 pixels per meter side, equals 1 mm = 1 pixels, and 1 cm = 10 pixels, in perfect reference . . This means I can control the game across, all models, so they get a pixel resolution of CLOSE to 1 cm x 1 cm has 10 x 10 pixels, on EVERY surface, if that makes sense . . .
Then I take a texture with the same pattern, but larger, and put it on the unwrapped model, maybe it needs to be a 2.5K texture, with the same grid, then I scale all the UV’s, until the 3D model next to the reference texture - plane, has the same size, of the squares, and then I know I’m looking at the ’ same ’ number of pixels, per model surface, and that my model has a standardized ( almost ) concentration, of 10x10 pixels per square centimeter, which is a nice unit, or standard, so everything it mathematical, accurate . . .
Note, the pictures are from some tests, where it didn’t work so well, the point is, using this stuff, one can make sure, every model has about the same number of pixels, per length, or area, standardized, across the entire game, good visuals . . . 
<3 <3 <3 And, it’s nice to know everything is math, well build, standardized and, accurate, to real world standards, lengths, surfaces, all that stuff, is beautiful . . .