Each paper has its own instructions with recommendations for writing an article, including explanations for the design of graphic material. If you cannot find it, I recommend you to download and study several recent articles published in the journal you are interested in and written by a well-known author (it is easy to find by a large number of citations). Usually in such articles, all requirements are met. You can also look at the design in other papers, for example, in the "PRL" (http://forms.aps.org/author/styleguide.pdf)