Hi,
You can find the setting at customizer > layout > Woocommerce. Make sure the Woocommerce module is activated at appearance > GeneratePress.
Oh, my bad. Didn’t know that the settings are to be found under the layout panel. Awesome! This also fixes the issue with the smaller width. While the standard settings were set to “no sidebars”, the setting for the shop page was still at content/sidebar. This is why the content area was decreased to only 70%.
You saved my day. Thank you very much for the great support!