My name is Lizzy and I’m from the support team at Shopify.
If you'd like to reorder your variants you can do this within the product pages by clicking on More actions>Reorder Variants.
Here you will have the option to choose how your variants are displayed to customers.
If you'd like to give customers the option to select one option and then the other you could set this up within your theme if you have the variants in the product. A theme like Brooklyn gives you this functionality.
If you have more variants the 100 pre product limit, you could use a product options app like Infinite options or Bold Product Options, to create this flow for your customers. These apps give you the option to add checkboxes or conditional options to your products.
Does this help with the set up you're looking for? Let me know if you have any other questions about it!
Thank you, Lizzy
Lizzy | Social Care @ Shopify - Was my reply helpful? Click Like to let me know! - Was your question answered? Mark it as an Accepted Solution - To learn more visit the Shopify Help Center or the Shopify Blog