I'm a professional illustrator, so if I were drawing these kinds of images, I'd probably sketch out the linework very carefully and lightly first, then going over it again once I established the lines with whatever medium I was working with (marker, paint, pencil, pen, etc).
Yes, you can definitely use a French curve or maybe try a Flexible ruler which cost about $10-20USD, depending where you shop.
They are great for just sketching the linework out to finish later.
I do recommend practicing a lot, first, to get your hand and the muscles in your hand/arm to move in the ways that you want to draw.
Just my thoughts. Good luck!