Currently, the Onda v919 is shipping as a single OS tablet. But now Onda have released the files need to convert your v919 3G Core M into a dual boot. The dual boot bios, Android 5.0 Rom and Windows 10 image are now in the downloads section of the Onda v919 3G Core M downloads page.
Onda claim the AnTuTu 5.7.1 score is in the 60k range, not a bad score.
You can find the downloads on the 3rd tab. You need the bios, Android Rom and later the Windows 10 image. I’m trying to download this myself for when my v919 3G arrives for review. But I’m not having much luck.