Full android backup

This would only work if the devices were EXACTLY the same make model and configuration. And you'd have to have root and custom recovery installed on both.

If the devices are even slightly different it could brick them.

 

Same memory, too? Same hardware versions? It could be tricky.

if root is possible you need to root both and install TWRP. Then you take a full nandroid backup on the source phone (which is an image of all existing partitions) and then copy the backup to the destination device and restore it.

If I may ask, why do you want a complete image? With a decent backup plan restoration to the new device would be less hassle and you'd by 99 44/100% restored.

 

If you are going to deploy them like POS displays and intend to have them all registered to the play store using the same account, I think there are actually management systems to do that that would make future updates and management easier, although I don't know specifically what they are.

I don't think rooting is a practical solution for deploying a large number of devices and it certainly isn't secure.

 

If you are removing system apps and adding your own, then you'll definitely need root.

If root isn't readily available for these devices, then this whole discussion may be moot, unless the manufacturer is willing to work with you in modifying the stock ROM for you. If I may ask, which devices are we talking about?

 

I can see three problems right away.

First, off brand devices generally don't have a huge development community so custom recoveries might not be readily available. You'll need TWRP to create the image from the base unit and then you'll also need it on the others to deploy the nandroid (the backup image).

Second, these things ship with Android 7 (Nougat) which means its going to be harder to root, if you can root at all.

Finally, the process to flash the stock rom should something go wrong may not be freely distributed by the manufacturer.

Do you have one to play with? I'd recommend testing before you commit to anything large scale.