There may be some javascript plugins you can add to your site but they come at another risk. The best options is to fix the issues you're having. Typically, these are issues with your overall design, layout, css, html, cshtml that you'd have to modify. Page Speed Insights really breaks down the elements on your page/site that have issues. I'd start there.
LCP can be directly related to the images/videos the content editor is loading in the CMS. If you aren't optimizing them prior to output then it will cause problems.
CLS is related to elements shifting up/down and side to side because elements are loading at different speeds/times and causing the other elements to move in while the page loads. Again, PSI can provide you details on the elements where this is happening, but typically preload your fonts, preload any less important css, load your js in async or defer mode.
Best thing to do is as I've mentioned already, check out Page Speed Insights details and inspect every element in the report they provide. There are links on how to resolve issues but maybe not so much where the actual problem is in your code.