First it would be great if you can share some of your code, tell us how your project is structured so we can give you proper help.

Without knowing the structure of your pages and if your pages are composed by components. I recommend you to create components for the code that's using React hooks or accessing the window object, as small as possible so you can mark them as client components with the 'use client;' directive.

Having SSR will benefit your users as most of the code will be rendered on the server and the browser won't need to do much work to make your app work