WooCommerce design change issues

Hi legends! I'm having a bit of trouble editing my shop page for WooCommerce on my site.
I'm trying to change the size of the thumbnails for starters, and the fonts. I can't find where to do this if that option isn't possible in the theme customisation page.
But doing something on the page like changing the banner doesn't seem to show up when previewing the page. Probably two separate issues though.

Can you help? I've granted support access.

Cheers, Tom