Asking for recommendation letters for math PhD applications Fall 2018 application cycle has started and I have a couple of (hopefully not too specific) questions regarding recommendation letters. I am applying for a PhD position in pure mathematics in the USA, with lots of top schools included.

(1)  Does the status of the letter writer matter greatly to admission committees? For example, I have done research with a full professor, an assistant professor and a lecturer in my department. The latter two got their PhDs in 2011. If the three of them write me a letter, does that automatically put me at a disadvantage because two of them are not full professors or one of them is a lecturer? I have heard that, in principle, letters from people that are known in their field are looked upon more favorably by committees, particularly because they might be familiar with the letter-writer and can 'read between the lines' and get more information out of the letter.

(2) Should I bother asking for a letter from professors that only know me through classes? I have a potential fourth person in mind for a letter - he is a professor I took two classes with and did well in both. In my understanding, "so-and-so was a good student in my X and Y class" will probably impress no-one, even if it comes from an established professor. All programs require 3 recommendation letters, so would you think it is worth the effort to have an extra letter if it comes from such a professor?

Thanks in advance for any responses.
Many, if not most, successful PhD applicants in mathematics have no research experience, and even when an applicant does have "undergraduate research experience, " it's usually not worth much as an indication of talent. If the first three letters are from the same project, it's probably better to skip one of them and go with the course professor instead. Rank, or at least reputation, of the recommender does matter, but what's most important is what they have to say about you.