I did some trial and error and understand this now.
ReadyMode replaces the Sleep mode. Whenever you ask Windows to put your PC to sleep (either by a timer or manually), the system will instead go to ReadyMode.
There's a setting in BIOS to change the power/blinking behavior of the power button in ReadyMode, so that you can easily know whether the PC is awake, in ReadyMode or Sleep.
1. SMB file sharing works. I can access files via SMB mapped drives from other PCs while my NUC is in ReadyMode
2. Deluge Daemon works
3. Using teamviewer, as soon as I connect, the NUC comes out of ReadyMode.
So far I like what I am seeing, I just don't understand how everything (including un-supported programs) work in Ready-mode.