If AROS and UAE are a priority then x86 hardware solutions are the way to go.
Not just because of the hardware advantage, but software wise x86 offers better choices for both, AROS having best support under x86 and uae having the best versions under x86.
Im quite fond of my baytrail tablet. Only portable device I've used that runs any Amiga software I've thrown at it at full speed.
For a super cheap option a PSP is surprisingly capable, but unfortunately Amiga emulation is too slow.