Dear friends
apple I phone 7 is very smartly phone.I had this with my iPhone 5. The sad solution was that one microphone was broken and changing it would have costed 80€. But when this is iPhone 7, you still have guarantee so I would call Apple support and then I think they will give you a new(refurbished but at Apple, that’s as good as new) one in Apple store.
Also, these low performance cores are much smaller than high performance cores. iPhones perform best because they have less and bigger performance cores. Many other things are also important for performance, like storage speed(where Apple also is the leader with newest NVMe storage) and gaming performance depends on graphics card and resolution(the lower the resolution and the more powerful the graphics card, the better you can play a game. Another example where iPhones are also leading.