OPTIS Product Options, Variant

Works great! Much easier to set up than other product variant apps I tried, and a quick message to the team removed the watermark that says "Powered by Optis Product Options."

I installed it to be able to set a total qty regardless of variants ordered by customers. This relies on Shopify for total qty, and the app to set your no-charge variants (there's a paid option for the app if you'd like to set individual prices for the variants, but maintain a total qty)