iMEDwriter: The review papers are the longest papers and it might reach to 5000 words and 100 citations, although now some journals suggest shorter ones. While a narrative review has not an standard format and after and introduction, the rest of paper has no specific format, a systematic review has an structure the same as an original paper.
Also a review might have an statistical job, so called Meta-analysis that is done when the review question is answerable quantitatively. Each review need to be comprehensively reviewed all studies with the same objective and might need quality assessment and quantitative synthesis. Formerly, it was suggested that just seniors can write reviews, but now some talent juniors do it by following the guidelines. If you have followed this steps you might want to get a free quote from me about your review:
Writing a systematic review is a good start for each researcher to understand what is happening in the field