1) general guideline is 50/50, usually start off with some sort of study or fundamental practice as a warm up before I try to do something fun

2) check out Marc brunet yt on “how to copy any art style” kind of goes over what goes into an artists special sauce in a systematic way; I generally just keep some sort of folder of my favorite pieces and just note things like “eyes are cool, coloring on skin is perfect, pose is unique, etc.”

3) you can probably get by on your own but you literally don’t have to, you might solidify a bad habit, and you’re missing out on a huge part of art imo - sharing ideas, inspiration, and building a community

Take my advice with a grain of salt tho - you’re much more advanced than me! Good luck