There are 3 weight classes in the game. Light, Heavy (Bella, Beowulf, Eliza, and Parasoul), and Gigantic (Double, Big Band). This largely dictates their falling speed while being comboed.
While experimenting with combos, it's easiest to pick Valentine, Parasoul, and Double as the enemy dummy team. Once you have a baseline, you can begin experimenting with the rest of the cast, but keep in mind that it's possible things may drop on only 1 character quite often due to hitboxes (Squigly's thin and floaty, Painwheel and Bella are short while standing, Bella is wide, Double is extremely short while crouching, Big Band is Big Band, etc).