milo695 I generally only use it on sites that have paid for optimization services, otherwise I would only setup basic caching on a customers site.
My usual config is to turn on as many fixes in the General tab as possible. I usually can't use the xml-rpc fix since so many external services need it. Then on the Assets section I would turn on Defer JS and Delay JS and set to "delay all scripts" (if that breaks anything, then you just need to add the name.js of whatever broke on the site, like if the mobile menu breaks then you can search the source code to see what js file in the theme relates to the mobile menu and add it in to exclude mob-nav.js or whatever), then I enable Remove Unused CSS which I try to leave at Defaults but if it causes too many issues on the theme then you can use the dropdown to set it to asyn. Important at this point to clear all the caches and load the site in an incognito browser to see how its loading, including with mobile view in the incog window.
In preloading I just preload 1 critical image. Then in Lazy I turn on images/iframes/thumbnails/missing dimensions fix. I will exclude the mobile logo in there from lazy loading, and I'll usually set it to exclude the 1st image from lazy loading in this section as well. In Fonts, I'll usually hit Disable Google Fonts, it's impossible to get good LCP with custom/external fonts, really want people to just use system fonts if they want to get great core web vitals scores.
Sometimes in some themes you'll get an issue with the mobile version not being very quick to open menus or links, like it lags, especially on iphones. You can help it by going to the Tools section and enable Advanced Options, then in the Assets section you can turn on FastClick.
After all that, the only thing that's needed is basic page caching, which I would get from something like WP Fastest Cache. I like Fastest because it's extremely simple, lightweight, AND it has some CDN integrations available like CLoudflare so you don't need yet more plugins to clear the CDN.
