Font size, font style, paragraph style, margins etc do not matter at all. On acceptance, your manuscript will be stripped of all formatting anyways (except italics for highlighting).
The only thing we would ask for is to use the Heading style to indicate the hierarchy of headings (H1, H2 etc). But again, the font, line spacing etc does not matter.
Feel free to submit your manuscript "as is" without worrying about formatting too much, at least for the initial review round.
After acceptance, a professional copyeditor will help you to clean up your manuscript.
We do know that many reviewers prefer to see line numbers, so if possible, please enable this feature/