Default Are ROMs for Chinese phones compatible, given functionally identical hardware?

Here's an example:

JXiaoMai MOTE3, MTK6582 5" 1GB

No-name "M3", MTK6582 5" 1GB

On paper they're fundamentally the same down to the details, but I like the shape of the M3 much better - I've always preferred square shapes to the Samsung-like rounded-corners design. But the M3 runs Android 4.0.3 which is outdated to say the least, while the "MOTE3" runs 4.3.3. Are the ROMs for generic clone-phones specific to the model, or can I hope to find a 4.3.3 ROM for the M3 - or a similar enough phone that it'll run on the M3?