I recently started learning modelling so I can import it for my ThreeJS project, so I was wondering is it better for performance to use n-gons or to use quads to model object?
At the end of the day they will all boil down to triangles. Triangles are the most universal polygons in 3D graphics.
In your modeling application it’s fine to work with either though. Whatever makes your life easier as the artist, I think people tend to like quads . When you export to glTF, any quads or n-gons get converted into triangles automatically.
Related guide:
https://cgcookie.com/posts/guide-to-clean-topology#question_2
It’s also noteworthy that ngons with holes or inward extrusions can lead to errors without sufficient edge supports when exporting to gltf format