Can I use the plugin in test instances such as dev or staging?
Yes you can. The site licenses allows the additional usage of the plugin in your test instances such as dev or staging.
How is this plugin different from other group attributes plugins?
While there exists plugins with a similar feature set we tried to create a version from our own vision with best-in-class features. Among them are a super fast loading of group attributes in the admin area when editing products. Further the rendering of layouts happens with containers and headers and is not solely table-based which gives much more possibilities for unique page design. And you always have the possibility to create your very own template.
Unfortunately there are some technical limitations, mostly due to the nature how WordPress and WooCommerce are structured. Hopefully one day they all will get resolved.