Assuming you have all your scripts minified already ( probably even then) the biggest speed improvement will come from using fast servers for hosting all your external scripts.
For instance, if you are currently using dropbox it will significantly slow your site.
I’m extremely happy with Amazon Cloudfront for hosting scripts and even gifs I use inside custom script. Even just Amazon S3 is pretty fast.
Can’t say much about Prefetching. though it looks interesting. Definitely gonna check that article out.
@nathanphilsteele What’s the site? I have several CMS sites in action and they are all performing very well. I don’t have massive data in them at this point but as I’ve added more nothing seems to be slowing down.
The site loads decently for me as well. According to https://website.grader.com you have around 103 requests which is a lot. You have a larger number of fonts loading but I don’t think that would really be an issue. In the debugger it looks like there might be an issue with a script. Could you try removing that script and see if it helps?