Doing some tablet/mobile research & picking one

[fivefeet8]

It's going to be difficult to find anything specific about those devices as they pertain to PPSSPP. You can go by what their benchmark scores in other areas to compare at best. In General and not all cases, Intel HD GPU's have comparatively inferior OpenGl drivers. On an Android device, you can only use the OpenGl render in PPSSPP. Anything with an Intel Atom CPU will generally have an Intel GPU.

Imagine Tech GPU's have more problems with rendering in PPSSPP because they are tile based. But this could be overcome with updates to the emulator. Out of all the devices you've listed, the Mali 450 is probably your best option at the moment.