To provide accessible but also usable web interfaces to people with low vision (PLV), academics and regulators provide guidelines in the form of adaptation techniques, as well as adaptable interfaces. Following these recommendations, practitioners developed mainstream solutions such as the Microsoft Immersive Reader. With this kind of solution, PLV can adapt or customize web user interfaces in terms of style and structure. This study aims to explore the adaptation carried out by PLV. A mixed methods research design, including both accessibility and usability concerns, allowed us to capture the user interactions, observe them, and access their expressed perception of usability. Findings show the universal nature of mainstream solutions does not support the diversity of PLV. We believe that universal adaptability features better benefit users with less severe and more common visual impairments. Finally, we discuss potential improvements and future work to support a wider range of PLV.