Integer operations work well regardless of AMD/Intel. Again, AMD provides peaky performance. Not an issue and can be quicker in non-realtime video encoding, but the peaks and dips make them unsuitable for a real-time, production environment. There's a reason serious streamers use Intel based rigs. Newbies get in with AMD, thanks to the lower price.
'Everyone overclocks it'? No. You compare apples to apples. An i7 with a proper overclock will see further gains, due to already higher efficiency cores. AMD starts out chucking more cores and clockspeed at a problem in the first place. Pushing it higher will extend that performance, but to get past the top of that short hill, you need a more efficient core. Which AMD hasn't bothered overhauling for a while now, as they're focused less on top-tier performance, and more on the budget-minded consumer.
Yep, Unity is pretty well known for being a poorly-coded game... almost on the levels of BF4, ArmA III, or Arkham Knight.