So guys just out of curiosity and in case anyone else ends up with the same weird pop noise coming from the top case, I discovered what was happening. And it wasn't the fan.
I tried disconnecting both fans and the noise wouldn't cease. Then I tried turning the machine on with the bottom open and I realized that the noise came from the heatsink.
It all makes sense now. When the chip gets hot due to Chrome or Photoshop, fans kick in and that's why I thought they were the culprit. However after ruling them out, I tried pressing down a bit on the heatsink only to find out a couple of screws were loose. Both the type that connect the heatsink to the case and the ones that push the springs down the chip. After tightening those out everything seems to be fine. At least for now.
It makes sense the chip would go from cool to hot very fast, thus making the fragile screws+spring vibrate and pop. If the noise comes back though, I have no idea how I'll solve it haha