Is it more likely for graduate students to visit relatives in the United States or a tourist visa?

If you have relatives in the United States, it is easier to apply for visiting relatives than traveling, and it is easy to be rejected. Applying for an American visa does not mean that you apply one or two months in advance this month, but many days in advance. It doesn't matter whether the application is finished or not. Visiting relatives or traveling in the United States is a ten-year visa, so you can apply now. If you graduate, you'd better have a stable job, which will be easier.