Hello,

There is no option that you can control the size of each category in the categories element. Only the option to set layout is available. The size of the categories items depend upon the thumbnail width and cropping that is set from Appearance >> Customize >> WooCommerce >> Product Images.

Screenshot for Clarification: https://ibb.co/41DLvXk

You can set the cropping according to your needs.

Best Regards.