Hey baeshick, sorry it took me so long to get around to this!
I don’t feel like I’m the most qualified to give an answer, I’m still in the middle of learning all this stuff myself, but I’ll give you a start at least, haha. Human anatomy is one of the most complicated things to learn, we see humans every single day so it looks strange when something is even just a little bit off. At the same time, realism can be incredibly time-consuming and isn’t everyone’s cup of tea, so stylization can be a good thing to think about while you’re working on learning human anatomy.
My main tip is just to practice from life as much as possible. I know it’s kind of “the” advice for learning to draw, but it’s especially important in this context. You want to have a good grasp of the human form before you start trying to freestyle with it, because if you don’t have a solid foundation your proportions will feel unbalanced and the poses will feel forced (I’m still struggling with this, myself.) Figure drawing classes are going to be your best friend in learning this stuff, honest. Keep an eye out for places that offer figure drawing sessions and use tools like croquis cafe (nsfw) when you don’t have access to live models! learning to draw the human form quickly is much more important than getting the details down- you can always build the details on top later. I recommend getting as close to the real thing as possible, there are some sites that use digital 3-d models for figure drawing which can be useful, but are going to have inherent flaws in the translation from the original.
Figure drawing will also help you pinpoint which details you need to focus on to get a better understanding of. You’ll realize that the arms consistently look off, or you can’t figure out how to tilt the face in different directions, or you have no idea how to make that foot look the right size compared to the leg. This is where you start to get into the nitty-gritty stuff and start really focusing on improving your weaknesses. Choose one thing at a time to work on understanding from the inside out, study the musculature and spend some of your figure drawing sessions JUST drawing that thing instead of focusing on the entire body. Once that piece makes sense to you, come back to the full figure and you’ll find it’s much easier to draw it in a quick and readable context. Of course, then you’ll notice this /other/ thing that’s consistently off in your figures, and then you can start from square one with the next area of focus.
I also suggest looking at lots of different models during the process. Drawing idealized figures is a lot of fun and definitely a good way to learn musculature, but variety adds interest to your work and helps you stylize! As you build your knowledge, you’ll understand how to better push the boundaries of the figure while still keeping it recognizable and proportionate (and your characters will ultimately be a lot more relatable.)
That all being said, feel free to take this with a grain of salt and don’t forget to break away from the study to just have fun with it once in a while, otherwise you’ll start to feel stale. It’s a tough subject, but I hope this helps! Good luck!
Further references and recommended reading!
Artists to follow (I’m positive this list is severely lacking, but it’s a good start):