I do actually have video capture comparing how the old and new layouts run, but the file limit for forum posts is too small to upload it. I'm on firefox, with a typical uBlock + Ghostery setup of extensions for adblock (along with a handful of other misc. plugins that shouldn't be relevant) and none of these have ever seemed to have an affect on how well pages run before. It seems to be an issue on virtually every page using the new layout (Game homepage, the search box/search results page, and the larger "mods" pages (ie https://www.nexusmods.com/games/skyrimspecialedition/mods) are where I've personally experienced it).
Basically, scrolling up and down the pages is very jumpy. Instead of scrolling the wheel and the page moving smoothly, it is slow to start moving and then moves at a noticably low framerate. This "lag" as it were also applies to opening/closing the search box. Pages load perfectly fine, the only noticable drop in speed when it comes to pages opening is that mods take slightly longer than they used to to appear on the search result page, but it's fairly minor.