I don't know the reason why the sync was to W10 instead of my Desktop 8.1. All three, laptop 8.1, W10 and desktop 8.1 have same account info. . Guessing here, if I changed my desktop background on any machine, the other two would follow? I guess I should have a different account for each machine? or just not sync.
What gets synced depends on what the settings are on each device. I have some sync settings turned off as I don't want my tile layout synced from my laptop to my desktop. They have two different sized screens. What device you were last on, and what you did on that device can affect it too. Like changing your wallpaper etc.
Yeah, if you change something that is synced, its not synced until you actually turn on the other device, and then only if its set to sync that feature. Normally I sync my theme/wallpappaer but decided to turn it off on my Windows 10 PC. I remote desktop into it. It makes it easy to see it at a glance on my three monitor setup which screen is the Windows 10 PC. There is one feature of sync I really like. My favorites in IE are synced to all my PC's. If I bookmark a site on my laptop its added to IE on my desktop the next time I turn it on. Web Site passwords too, if I click remember this site. No having to log in on every PC if I switch devices during the day. It also backs up your settings even if you only have the one PC. On a clean install once I log in with my Microsoft account, all my synced info is automatically restored back. IE favorites, theme, start screen layout and tiles, etc, etc.
Quote