It's possible that using high quality templates in your project to give it visual interest might make your project more "engaging" for your stakeholders, giving you a competitive advantage. Templates can raise the perceived professionalism of your project: The same way that a suit might make you appear more professional when going on a job interview, the use of project templates can make your project appear more professional.
Try not to make your paragraphs longer than 3 or 4 lines. When your paragraphs are short, people will read them easily. But if they are long, it will seem overwhelming to people. The colors you use in your newsletter design is important as well. So you should know a little about colors psychology. It's not hard. You must already know about the effect of every color on people, before designing or choosing your newsletter template.