i wanna add an adendum to the anatomy thing which is: you dont need to draw in a style with semi-realistic proportions in your comic - and simplifying the body is a good way to speed things up. but knowing this stuff makes it easier to simplify the body, and doing life drawing and anatomy studies is a great way to train your hand and your eye, making everything go faster and smoother. so no matter your style, practice life drawing - but dont feel tied to semi-realism. (talking to OP ftr)
also, when it comes to making fast but pleasing comic art, your big three are:
- composition
- gesture
- colour / value
compose things dynamically and clearly, with good flow, and itll look great. perfect gesture and your characters will be full of life. get a good palette and good contrast and your colouring process can be just 3-colour flatting and itll look super!