@thor Try that!
I still think something's wrong with OBS, this is a quad-core i7 for god's sake! I bet it builds Firefox in minutes, encoding video isn't rocket science, it shouldn't be able to put such a machine down to its knees!
Using wireless network might have contributed BTW, sometimes hardware cryptography is broken in wireless adapter and it gets offloaded to the CPU by the driver, did you try using wired? Just an idea.