Yes, it can be disabled. At least on my rM1 I've managed to disable all cloud syncing. For me it's very strange idea to put any personal notes in some cloud.
The other thing to disable is sending some stats info to their server enabled by default to my surprise. It can be disabled with terminal through ssh and I did. Can't find though the article with detailed instructions.
Yes. AFAIUI (haven't received mine yet) it's not required in the first place. You could likely unlink your account from the device though, if you already signed up. You can even edit the hosts file on the device to just block connections.
You have to enable it explicitly. There are also several third party tools for offline syncing, and there is always the option to SSH into the device and do whatever you want.
