UX testing for multiple product mixes

I am charged with testing a product mix change that takes what was 5 individual products and turns them into one product that can be incremented to approximate the previous set of 5 products.

I am already conducting quantitative research through surveys around the existing & new product offering. My validation solution is to prototype the new singular product offering and conduct qualitative, in-person, moderated testing with the specific demographic of customers.

However, I'm wondering if there are any other methods of validating the new product mix that one might recommend outside of this.

Any thoughts?