Hi Luke,
WC Vendors, and WC Vendors Pro, do not care at all about the size of your uploads. That in fact, is a PHP setting you need to look at.
https://wordpress.org/support/topic/how-to-increase-the-max-upload-size?replies=17
https://wordpress.org/support/topic/how-to-set-maximum-upload-file-size?replies=15
http://www.wpbeginner.com/wp-tutorials/how-to-increase-the-maximum-file-upload-size-in-wordpress/
https://kinsta.com/blog/increasing-the-maximum-upload-size-in-wordpress/
http://premium.wpmudev.org/blog/increase-memory-limit/
Ben