Why's that? The initial Fusion leak said that the Fusion handheld would run ARM. That leak did however say that the Fusion Terminal (console) would run an IBM PowerPC processor, which doesn't appear to be the case with whatever AMD is currently working on, AMD is making it sound like it's a full AMD chipset, so both the processor and the GPU are AMD, same as PS4 and XB1.

I don't think Fusion is going to be quite what some people are speculating it will be. I see alot of speculation that both the console and the handheld will play the exact same games but with better graphics on the console. I'm not sure that will be the case. Certain games will likely release on both the handheld and the console (mainly 1st/2nd party games), and they will probably be cross-buy, but I think they won't be the exact same game, there will be differences between the console and handheld versions because each version will be made specifically for that platform for optimization reasons. You'll likely be able to use your Fusion handheld as a Gamepad-like controller for your Fusion console, and you'll be able to stream your handheld games to your TV through the console.

Many 3rd party games will likely release on just the console since developers won't want the low specs of the handheld holding back next-gen graphics (the chipset rumored to be in the Fusion handheld is a bit less powerful than the 360/PS3). I think Nintendo wants the console to be running a similar but more powerful chipset than PS4 and XB1 so that 3rd party devs will easily be able to port between the 3 systems. Sony and MS will likely stick with AMD chipsets for their 9th gen systems when they release in a few years, so Nintendo's next console will still be easy to port to even if it is less powerful than the PS5 and Xbox 4. Nintendo wants back the 3rd party support they lost with Wii U because they didn't listen to what 3rd party devs wanted (3rd party devs wanted x86 but Nintendo went with PowerPC instead). 

It's possible but the lowest TDP on an AMD x86 chipset as of now is still pretty high, I think that chipset is made for large tablets, could run a bit hot in a handheld and give it a short battery life. AMD could be working to improve TDP on a new chipset though, they might manage to make an x86 chipset with a low enough TDP to be used in a small handheld. 

Hopefully. You never know with AMD though, they're not as good at perfromance per watt as Intel and Nvidia are. 

I just hope that the new handheld falls somewhere between Vita and 360/PS3 in terms of performance, at least.