Hello, @TFS,
1..Once you edit the banner block from the banner image settings you will be able to edit the image size as per your need. Check the image: https://postimg.cc/nMNbSVwJ
2..You can get the size of the banner image. Actually, the image is in the WordPress gallery you can navigate to the Dashboard >> Media >> Library and check the banner image details by clicking on it like this: https://postimg.cc/Z0BxHJdp
3.. Actually, for this you have to create multiple single product layouts by navigating to the XSTORE >> Theme Options >> WooCommerce >> Single Product Builder check image: https://postimg.cc/gxsG7FZH once you click on the “Create New Template” simply enter the name of your template and set the condition of the template to appear on which product like this: https://postimg.cc/d7XcMqtr and now create your custom layout for the products you set the condition for.
Regards 8Themes Team.