Budget Car Rental "Or Similar" Headaches

Hey everyone, I read a few nightmare post of car rentals and not getting a car close to what was reserved. This is my first time renting so I want to be prepared in case my luck runs low. Going to Maui in a week and rented a Standard Sport class "Mustang Coupe or Similar". Issue is, I haven't really heard of Maui ever having Coupes but only convertibles which makes me uneasy. So I feel I will be given the "Or Similar option", should I expect it to still be a sports car? What hassle should I be ready to deal with? Thanks in advance!