Taylor & Francis publishes some articles "online first" before they are assigned to a particular issue and page numbers are added. They thus have page numbers starting at 1. I have access to the PDF of such an online first article, which is now properly published in an issue of the journal (and thus has page numbers starting with 601). The length of the article appears to be the same (16 pages). As I don't have access to the published version but need to quote a sentence from p. 14 of the online first pdf, which I have, I was wondering whether I could just calculate the new page numbers (so p. 14 would now be p. 614) or whether the typesetting changes when an article is added to a journal, making this method unreliable when citing.
Note: comment converted into an answer.
Based on my personal experience, the typesetting used in the "online first" version should be exactly the same as a final published version (only page numbers change).
At the very least, I have yet to see a case where the page layout changed. So I think you should be safe. If it's a very important citation, it might nevertheless be a good idea to try to get a hold of the final paper, just in case.