All editors and major publishers use style guides. For instance, I use the The Chicago Manual of Style because I learned how to write in a journalism atmosphere. Different people use different rules of style, and they are - for the most part - all fine. The important part of style is consistency. Meaning, find a style rulebook and stick with it. Many people use Grammarly but it is not the end all for style and grammar, just one of the cheapest. There are multiple and accessible rule books for a particular type of writing style, and finding what works for you can take some trial and error.
What you are probably wondering is how to improve your writing tone, or how to make your prose move up to the next level. The best way is to read books that are known for their universal appeal in tone and quality. Some authors I typically recommend include Charles Dickens, Mary Shelly, John Steinbeck, Raphael Sabatini and JRR Tolkien. And you don't just read them, you make an effort to understand how each author turns phrases into meaning and WHY each of those lines or paragraphs resonates with readers more than, say, the latest badly translated LN out of China.