I really hope the APUs can use 4+GB of RAM if you tell them to.
Honestly, the progression of Intel's iGPUs over the years makes me pretty hopeful.
If you compare one of the first iGPUs to the current 'top-of-the-line' mobile iGPUs, there's not even a contest.
+1,609% on userbenchmark.
Intel has lately de-ephasized desktop iGPUs (much to my dismay), but even comparing my i7-4790K's HD 4600 to the Iris Pro 530,
there's a +21% difference. Which might not seem like a lot but it honestly is.
What's really neat is you can actually overclock your iGPU if you have a K-series chip. Granted, you maybe shouldn't be spending on a K-series chip if you can't afford a discrete GPU but who knows what you're up to. (Especially on a SFF forum!) My i7-4790K can make Just Cause 2 and Resident Evil 5 playable at 60fps at 720p when I overclock it. Not knocking anyone's socks off, but not a complete pushover either.
If AMD lets us overclock their APUs (I don't know if they historically have), I definitely think it's possible to see ~750Ti levels of performance. 1050/460 performance seems a little ambitious but there's no way of knowing until we see what's up their sleeve.