The antonyms for the phrase "most freewheeling" would be "inhibited," "restrained," "restricted," "controlled," "cautious," and "conservative." These words imply a sense of caution or carefulness, indicating that the person or situation is not as wild or unrestricted as those that are freewheeling. Inhibited individuals or controlled environments may be afraid to express themselves fully, while a cautious or conservative approach is typically more measured and less carefree. While there may be benefits to both freewheeling and restrained behaviors depending on the situation, it is important to understand the differences between the two and consider which approach is most appropriate in any given context.