Ignore the horrendous design/color scheme lol, not much experience texture painting
Hey don’t be shy about it! The design is unique and interesting but most importantly looks like you’re having fun with it. Hopefully learning a lot as you go to. Keep it up 👍👍
In playing with your file it looks like texture painting in Solid viewport shading mode is basically the same thing I was doing in the video: Meaning texture painting one specific texture (as decided by selected texture slot) with a little openGL shading over it.

The difference being material preview displays all the textures working together according to the final material.