2. Steam, Cortana, update manager, etc, etc. W10 is notorious for having 50+ background prcesses going all the time. You can customize this to some degree but there are still essential processes you'll need.
3. No, you're still giving up some processing to Windows, Steam, etc. There's not a game that gives the full paper spec, PCs aren't designed to dedicate resources that way.
4. Win2 won't sustain 2.6GHz, it throttles down to 2.3, 1.6 or even 1GHz depending on GPU load and thermals. The CPU doesn't come at all to PS4 spec reliably. It's much closer to TX1's quad core A57s even, which core for core do almost match the Jag cores.
Core for core, the m3 7y30 is closer to the i7 3770.
And it's absolutely murders the Cortex A57.