latest armbian image entry suggests it can be installed on emmc, but it is not clear how to do that form the instructions included in google drive folder.
Is it possible to use titantools? If not, can i just unzip img.xz file and dd it onto emmc?
You can flash it to an SD card, then boot, then use armbian-config to write it to the eMMC. I used that to be able to boot off of NVMe. I would recommend not using the armbian image provided in the Docs as it is very broken, and instead compile it yourself using Armbian SDK (though the desktop will be very slow due to the lack of GPU drivers). I was able to get the desktop smooth, though I don’t remember how I did it unfortunatly.
armbian-config, got it. 
In what part the armbian image in Docs broken? it works pretty well with gpu driver support.