Is an approach different from perspective
The study of religion, also known as religious studies is an academic field of knowledge that focus on research of religion in its theoretical (philosophical background of the doctrine and ethics) and practical (cult, religion behaviors, etc.) aspects. You must explicitly divide religion studies and theology because their methodologies differ fundamentally.
The study of religion is a mix of social, philosophical, anthropological, historical and psychological analysis of the religion as a cultural phenomenon. Scholars who study religions must stay in the frame of unbiased scientific analysis. If a scientist practices some religious views, he or she should eliminate the possible influence of their beliefs on their research subject. In other words, if some scientist, let’s call her Jane study Islamic theology it doesn’t mean she is Muslim. Scientists whose focus is religious studies are not necessarily insiders. They mostly aim to explain the nature, causes, and specificity of religious beliefs. Why do people need to believe in God? Why is the cult side of their faith so important? How our daily life is impacted by the Christian ethic? Etc. For better understanding, you can read some of the research papers on this topic. Like this one:
The first thing you should know about theology is then it is a study of God. It also analyses religious theoretical background (foremost, of Christianity) but theology is always apologetical. It means, theologist would never doubt any of dogmatic truths. Among the aims of a theologist are the following:
There is a paper on theology explaining all these things in details:
So as you can see, a theologist can also be a representative of religious studies, but he is an apologetic insider, and his approach can lead to the radically different conclusions comparing to the researches who are not involved in religious practices.
In this case, theological approach, in fact, equals theological perspective.