A Windows Service is something you (generally) want running 24x7. In fact I think a Windows Service seems very much like the wrong thing to do here. Services are not the only way to schedule things in Windows.

And you can "just" use nssm to wrap any arbitrary executable with what is needed to make it a windows service.

edit: Windows can use Node and Playwright just fine. I think the only thing this needs a Mac for is to schedule and send messages as an alert.