I am curious about how competitive is publishing a paper in the United States' Proceedings of the National Academy of Sciences (PNAS) in comparison to leading journals in a field. Is PNAS on the same level as Science? Thoughts will be appreciated, but factual materials (i.e., links to research studies or other information on the topic) even more so. Do they consider/publish survey papers?
Additionally, I am interested in answers to the following related question. PNAS defines itself as a multi-disciplinary outlet, while my brief review of their editorial board left me with an impression of a strict field-based classification. Then, the question is: how one would submit a multi-disciplinary paper, in particular within information systems field of study, considering such classification?
The paper that I have in mind is a survey paper (or similar, i.e., position paper), based on my dissertation (its literature review, that is). The paper would cover the following domains: Economic Sciences (via ecosystems), Engineering Sciences (via software engineering), Social and Political Sciences (via ecosystems), Computer and Information Sciences (via software engineering).
Final question: does PNAS accept submissions from unaffiliated (independent) researchers?