Hi

Mobile performance is a very complex topic, and there's a lot you can do to improve it depending on the game type. First of all, let me note that the Duos has a pretty old GPU, so I wouldn't expect it to perform well with high-resolution fast-paced games like Fay Fire. Some devices where I've tested Fay Fire and it ran fine include:

HTC 8x ($150)
Nexus 5 ($360)
Nexus 7 2013 ($300)

The prices in brackets just to say that they aren't super-expensive high-end devices, just a bit newer than the Duos :)

Having said that, could you target a low-end device with WADE? Sure, I think we proved it with Zirma that ran fine on a sub $100 Firefox phone a year ago. How did we achieve it? Well, mainly by designing the game around the limitations of the target hardware. So for example: no assumptions about resolution (resolution increases with screen size), static screen that only moves on user input, all animations are tiny and on a separate layer, etc.

It isn't easy to design a game for low-end phones, but luckily there are a few tricks. The most likely cause for the slowness is the number of pixels you draw per frame. A lower resolution and a careful usage of layers can help a lot to reduce that. WADE has setResolutionFactor and setLayerResolutionFactors that will help you adjust resolution dynamically (i.e. if you detect an older or slower device, reduce resolution). There are many tricks that you can use, but ultimately depends on the type of game you are making.

Lastly, I'd suggest using CrossWalk for your android ports, rather than Intel XDK. Much faster.