alt Hacker News1MB is about the lowest memory usage you can get on Windows 7, because of reasonable tradeoffs made in the operating system to things like buffer and stack sizes. The OS creates a few threads for you, those threads have stacks and they didn't optimize the allocation size of those stacks - they used a currently reasonable default.
Depends on the app/framework but typically phantom threads don’t get started. Also, those stacks aren’t materialized until you write something - they’re all CoW’ed pages from a sentinel 0-filled page the kernel keeps around just for this purpose.