Thr 7840U is core config wise, the same as the Asus ROG Ally with the Z1 Extreme, just different clocks/binning. (Handhelds are drsigned for 10w handheld use, and 15-30w docked)
The 7840u is designed for 15-30w, but is meant for the 30w usecase. Other chinese pc handhelds like the Ayaneo Air 1s or the GPD Win 4 Pro already use the 7840u im their designs.