Generally a patch shouldn't tank performance but there's always a possibility and I believe it has happened. Unfortunately there's no way of knowing since every computer is different and they don't always update requirements for every patch/pack. Sometimes a single patch can tank FPS on any computer.
While this prepatch does add the necessary coding for the new EP, it doesn't act as if you've installed it already. The coding just sits there ready for the pack.
Windows 10/11 requirement is mostly because older Windows is no longer supported by Microsoft. Not that it won't work whatsoever with Windows 7.