I am designing a style guide for my project and read few articles that suggest it's a good practice to combine more than one style of typefaces to enhance user experience. May I ask how to decide the typefaces and how many typefaces should I use in my web interface? My main focus is to improve usability for very technical users who will access the website, but at the same time, I would like to take care of the look and feel of my website.
Typography on the web is a vast field which requires a deep understanding before you can make the right choices. There are two canonical resources on the web that are available for free:
You should read this article on UXplanet, it gives some good insight.