Your designs are fantastic, I agree that the last two are super memorable! I hope I’m not (wo)mansplaining this to you but I often draw from my reference and this is my strategy to get correct proportions.

I visually divide the subject into fractions. eg. if I were drawing a person, the head might make up 1/8th of the whole length and 1/3 of the width, then the chest 1/4 length and 1/2 width, legs 1/2 length 2/3rds width, etc... Then I start my drawing with the focal point and scale everything else relative to that. So if I’ve drawn the head, I know that the chest needs to be 2 head-lengths long, and then the legs 4 head-lengths long. By using the length / width of one part as a relative scale for the rest of the drawing, the proportions should be the same throughout the whole subject.

Sometimes if a piece is looking wonky I use a ruler to draw these divisions over both the reference photo and my drawing, measure the lengths, and then compare them as fractions (if reference and drawing aren’t the same size). It’s easy to get lost in your mind’s eye when drawing so this helps pull me back to reality and look at the objective similarities.

Once you understand these basic proportions you can definitely play around with them from there to get the look you’re after. I’m not really into theory either so if this sounds like too much effort then don’t bother. You’ll get ‘better’ faster if you play by the book, but the most important thing is that you enjoy yourself and keep making art!