WordPress and mysql

Hi,

first time user on the forum but not new to using wordpress.

I’m building a sports stats plugin, where teams can upload their scorecards via custom post type (wordpress basic post functions along with some custom meta box). I’m wondering if its best for the plugin to create its own tables? Or mysql wouldn’t be slowed down if i stored the stats in arrays in the wp_postmeta table?

I know PHP well and can work with arrays and extract stuff from mysql, but i don’t know much about mysql in terms of best practice in its design, performance etc.