Thank you for the kind words!
I've got some pretty hot takes on the process of coloring, which is my favorite part of a painting. Value and shading is a huge journey to understand, and there are a ton of things that will help you learn and grasp the concepts faster.
Let's start with question 1 - what's up with my backgrounds? I try to pick a more neutral color for the background than pure white, which has an influence on the mood/color temperature of an image. Overall the image should read well when converted to greyscale, this allows me to ensure the values are correct. I pick a background that makes the image pop the most, often as a last minute decision.
Which brings us to question 2 - do I use layer modes to pick shadow colors? Absolutely not. They've got their place in an animation pipeline and for some mild color correction, but separating light and shadow on separate layers for a painting is tedious, slow, and does not help you learn any faster. Reduce the number of layers, pick your own colors and actually paint instead of following these recipes straight out of a 2007 deviantart tutorial 
A whole character is often a single layer in my process, and I am a lot faster in execution because I don't have to click much - I choose a shadow color and I apply it, and correct it by painting on top if I need to.
Thanks again, and don't hesitate to ask any question you may have 
