I've been looking at performance for a few WordPress sites lately and came across a couple of interesting plugins.
Query Monitor - Shows database queries, API calls, object cache usage, errors, and CSS / JS scripts. It also shows memory usage to build the page.
Debug Bar - Show a lot of the same things. It's not been updated in a while, so I don't know if it's still active, but people still find value in it.
While helpful, it looks like the amount of JS, CSS, and unoptimized images are a bigger issue for these sites.
Next steps will be looking at LiteSpeed Cache to see how it can help with those. Would also like to find an image optimization system that can run from the command line.