These are the sizes of cutters, pastes and colours I used. I suggest printing out an image* of Cogsworth the size you want the topper to be. Check sizes of cutters you have before deciding on the size of the cake topper.
I had some leftover sugarpaste which I wanted to use that is why I decided to use a mix of sugarpaste and flower paste instead of plain flower paste. If I were to make Cogsworth again I would probably use plain flower paste ;) but perhaps it's just because I'm used to it ;)
*Image source: dribbble.com
(author of the illustration: Jerrod Maruyama)