By default Magento® allows grouping simple products without options only. In other words, Magento® doesn't allow custom options on grouped products. Using the Grouped Product Options extension for Magento® 2 you will be able to group:
- Simple or Virtual Products with options
- Configurable Products
- Bundle Products
Customer will be able to configure custom options of the associated products directly in the grouped product. This way you can create complex product sets where all products are configured on the same page. See example here.
In addition, you can convert the grouped product into a check-list, by replacing the QTY field with a checkbox. See example here.