I’d invest in a used x86 SFF PC over a RPI for performance, you will pick one up cheap and it’ll be way better suited for a media server over a RPI.
Look into Tailscale for remote access. Very easy to setup and their free tier is generous. (100 devices I believe).
With Windows 12 rumoured to be a subscription model, yes definitely. Enterprise will buy up the subscriptions, home users will look elsewhere. Apple will take its share of course, their products are too pricey for a lot of people though. Linux is the only real option for folks who value owning their data.