Two areas for improvement in terms of speed/performance is LCP, CLS and image handling.
<div class="p-body-main p-body-main--withSidebar ">. 0,16 CLS contribution. The first article on the grid. Anything over 0,1 is deemed to need improvements.
"Element moved 400px to the bottom", so the cause is the feature slider loading AFTER the container of the articles perhaps..
Youtube player always loads. https://www.youtube.com/s/player/4248d311/www-widgetapi.vflset/www-widgetapi.js. The feature slider has a media box where you can add YT videos, but I never use it. Either add an option to only load it once feature articles with media field active (better for users, but may be harder to add?), or just have a on/off button in ACP if you want to have this YT media function enabled or not.
Lazy load off screen images. (feature images that are not the front/hero image). If you have many feature article images in your slider, this can provide a sizeable hit to your performance.
Properly sized images for mobile/narrow. All images should have S/M/L versions to serve depending on the screen size of the viewer. This is critical for mobile performance.