I haven't spent enough time using the new layout to form an opinion on it overall, but I really, really dislike that I cannot type into the search bar without the entire webpage being obscured. I'm sure the new quick search has tons of improvements for browsing mods, but please consider that people often reference content on the webpage they are currently on when typing into the search bar. Moreover, the / key can no longer be used to move focus the search bar at the top of the page and is now merely a shortcut to the search feature. This is an accessibility downgrade because moving the focus to a predictable spot at the top of the webpage is the expected behavior in my experience. If you need a good example of what I am talking about, YouTube does this well. If the search box is focused with /, you can use tab and shift + tab to quickly move the focus to the major sections of the webpage. If you press shift + tab from the search box, it focuses on a hidden "skip navigation" button which moves your focus to the video results without needing to tabbing past account and navigation links.
I also feel the old searchbox with the dropdown results could exist alongside the new search menu. Sometimes while I am in the middle of reading through instructions or comments for a mod, I end up wanting to open other mod pages in new tabs for later. When I know the exact name of the mod page I want to open, the old quick search was more than adequate. My ADHD meds aren't strong enough to stop the new quick search from men in black mind wiping me when it takes over the whole page.