I agree with everything else you say, but you are mistaken here. The number of hours you spend tweaking Windows 10 is irrelevant - it is tracking you, regardless of what you do. You can make it better, certainly, but I would never consider it "secure enough" to be using for anything truly sensitive.

Even if you turn off all tracking and telemetry features, Windows 10 still tries to phone home a staggering 5,500 times in 8 hours. The additional use of third party tools designed to stop this did help a bit, but these researchers still reported 2758 connections in 30 hours.

Other researchers have similarly found that even when you disable Windows 10 features like Cortana, it is still logging your activity and sending it to Microsoft.