OP, based on what appears to be a very rudimentary knowledge of physics as applied to the handling of sports cars, I would advise you to read up on the subject.
It's troubling to read someone being wary of a Mustang because the "rear end fishtails". As if a company would build a car where this just happens...
If you're entering the world of sports cars you'll be doing yourself a favor to learn about the basics of vehicle dynamics. It will make everything a lot more fun. I'm not insulting you, just trying to be helpful!
Oh, and get a BRZ!
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Current: 2023 GRC Circuit Edition, 2012 C63 AMG P31
Past: (2) 2000 MR2 Spyder, 2017 GTI Sport, 2006 Porsche Cayman S, Supercharged 2013 BRZ-L, 2007 Honda S2000, 1992 Integra GS-R