Anyone who disagrees with you about this should buy a Mac and try not enabling iCloud. There's constant nags and as far as I could find, no way to turn them off.
2) that is entirely NOT true. You should install little snitch and see what happens even if you NEVER sign into icloud. note that the phone home contact is not immediate, it happens in the background at random intervals from random applications.
just some random services blocked by little snitch on a mac:
Tell me more about how dastardly it is that Safari communicates with Apple servers. Type it from your browser that doesn’t communicate directly with its developers.
I have an iPad (not iPhone or Mac). If you don't set up Icloud, there's always an annoying bright red circle in settings that tells you to "finish setting up your iPad".
Doesn't have to be bright red, or even there at all.
Last time I had that on a laptop I was going to wipe soon afterward and didn’t want to fully set up, I clicked the “finish setting up” link and canceled out. Voila, red circle gone.
2) I have booted macOS VMs without iCloud. I'm not sure of the nags though. I believe signing out of iCloud will prevent iCloud from contacting Apple.
https://support.apple.com/en-us/104958