I agree with the points that it has to be easy to read from a distance (because people are not standing right up to your poster) and I also add that one of the things that I have found is to not have too many pictures/diagrams in there (two maximum) because it is too distracting for the reader/viewer.
Essentially, the aim of a research poster is to visually represent the main findings, data, and overview of a research work. Similar to an oral presentation, a research poster is a powerful tool to emphasise your work by effectively presenting your opinions and findings. Therefore, the study questions and conclusions should be highlighted in an effective research poster, which should also employ informative graphics and visuals, have easy-to-read language, and more importantly novel findings.