ipq40xx tops out around 300 MBit/s (considerably less with sqm). Yes, ipq40xx is faster (CPU wise) than mt7621, but mt7621 has an extremely streamlined networking network design/ drivers - it can gain/ surpass ipq40xx in that regard for the 'simple' case, but that falls apart for more complex setups.
applies to your situation, meaning you should skip both of these options (in terms of mere APs, ipq40xx slightly tops mt7621a+mt7603e+mt7612 and might be more on par with mt7621a+mt7615n+mt7615n, while mt7621a+mt7905+mt7915 would surpass it again)…