So I am interested if there exist any general guidelines for how to evaluate/design a product form (create a style for a product). If so, is there any studies done that have shown that the results are positive related to product success?

I’d suggest also looking into conjoint analysis that breaks down specific styling differences between similar products - a start is the textbook “Product Design and Development” by Karl T. Ulrich and Steven D. Eppinger (McGraw-Hill 1995, 2000, 2004).

and on conjoint analysis - Conjoint Analysis

another book from MIT is

Urban, G. L. and J. R. Hauser, Design and Marketing of New Products, Prentice-Hall, Second Edition 1993.

The revision includes new material on designing for quality, reduced cycle times, prelaunch forecasting, quality improvement, defensive and competitive strategy, value mapping, the integration of marketing and engineering, new issues of organization, customer satisfaction, and new international examples. It is available in Korean and is being translated into Japanese and Chinese