I have this issue on a lot of my tablets, my friends have this issue too, so I don't know, why it's so hard to address this problem and why MS doesn't do anything about it. It was already a problem with Windows 8.
It's really easy, to "mess things up", so that Windows wont properly work on a tablet and will drain too much energy in connected standby. That still shows so easily, that Windows is still a desktop OS, and not optimized for handheld devices.
I know, that there are three "hidden" tools coming with Windows:
But looking on those, I don't see anything suspicious or "wrong". I know the fact, that the normal drain should be around 0.33 to 0.5% / hour on tablets, that's the margin for InstantGo/Connected Standby MS declares. But mostly all my devices drain about 1-2% per hour in connected standby.
I have nothing running on those devices, deactivated OneDrive (which isn't working too btw correctly and is still bugged under Windows 10, and if it's on, the drain is even worse).
I have disallowed the speaker/sound chip to wake up the device from standby, this a bug since Windows 8 and not fixed by MS.
One of my tablets has dual-boot and Android is running next to WIndows, and the drain under Android is normal/great compared to Windows.
I would welcome any help to find out whats causing the drain, thank you very much.