One feature that you may want to use is the No variant selected by default, which if selected, will force your customers to select a variant of the products included in the bundles to avoid bundle claims in variants that are not what your customers wanted. This is specifically useful for clothing stores or stores in which variant choice is important.
After editing that message and you save and launch your bundle, you can go to the page where you display the bundle offer. If you were to try to claim that bundle without selecting a variant, you will see a pop-up with the error text you customized. If you select a variant, the claim button will redirect you to the page you set by default in Settings.