My forum runs very fast and I am on a decent dedicated server, But when it come to installing / uninstalling styles and addons, it takes ages. Is this normal. I also hae a vbulletin forum and I could installed 20 styles in the time it takes to install one on xenforo.
XenForo does extra processing at save time to maximize performance at run time. It's a good trade. If you have lots of styles then saving can be slow. You should remove any styles and languages you aren't using.