A single main point doesn’t have to be kept to a single paragraph, especially if you are writing a relatively long research paper. Main ideas can be spread out over as many paragraphs as you deem necessary.
If you are writing a research paper for a class, consider the other students. Is it likely that they will also be writing about your topic? How can you keep your paper unique and interesting if everyone is writing about the same thing?
Who would be reading this paper, should it be published? Although you want to write for your professor or other superior, it is important that the tone and focus of your paper reflect the audience who will be reading it. If you’re writing for academic peers, then the information you include should reflect the information you already know; you don’t need to explain basic ideas or theories. On the other hand, if you are writing for an audience who doesn’t know much about your subject, it will be important to include explanations and examples of more fundamental ideas and theories related to your research.
Every type has a different aim. An argumentative work has to show a few sides of a particular issue and provides arguments in favor of one of them, a definition project aims to provide a clear explanation and analysis of one specific matter. Cause and effect research paper writing requires you to present a logical chain of causes and effects that relate to the selected issue, while reports simply outline a study (or studies) that were conducted previously. Interpretive papers are similar to definition ones. Compare and contrast ones, as a rule, describe the same issue from the perspectives of two different authors (scientists), while analytical research paper writing requires you to create a deep analytics of various opinions regarding the same issue.