"UC sells a product which must be priced as 10% of the total of all...

 Requirement Overview:

A product must be priced as 10% of the total fixed-priced products on the Quote.

 Solution Details:

Option A:

Setting the Pricing Method to Percent of Total ensures the price is calculated as a percentage of the total value of other products.

The Subscription Pricing is left blank since it is not a subscription product.

Option D:

Set the Pricing Method to List and Subscription Pricing to Percent of Total to achieve the same result with flexibility for subscription-based products.