Brand new rig experiencing terrible fps lag in games. Tried everything I can think of to fix it
Solution 1:
I just had a similar issue with my rig, and tracked it down to overheating. In my case, it was due to both accumulated dust and poor thermal coupling. The former is obviously unlikely for you but the latter can occur even on a new rig if the compound wasn't applied well between the heatsink and the CPU or GPU. Having too much high powered stuff in too small of a case can also contribute to heat in terms of reduced airflow.
If heat is the problem, the first clue would be your fans. If everything is set up properly, on a cold boot your system should be whisper-quiet, and the fans should not speed up until you start pushing the hardware. But if they're running full speed when the OS is idle, or take a long time to slow down after you're done gaming, you might have inadequate cooling.
You can also use a utility like HWMonitor to get readings on your CPU and GPU temperature sensors, fan speeds, etc. Most hardware runs optimally at or below 70°C, and exceeding 100°C will immediately cause severe performance degradation.