Most WordPress performance posts tell you to switch hosts and use a different page builder. That advice is correct and useless — you have a client, a deadline, and an Elementor site. Here is what actually moves Core Web Vitals on a project like that.
The image pass
Convert hero and above-the-fold imagery to WebP. Compress everything else with a sane preset. Make sure lazy-loading is on but not on the LCP candidate. Set explicit width and height on every image to kill layout shift.
The CSS/JS pass
Review what your caching plugin minifies and combines. Defer non-critical scripts. Identify render-blocking resources in PageSpeed and either inline-critical them or async them.
This pass alone moved Signature Cleaning's mobile performance score from the 40s into the 70s.