All components. And be specific. Brand and model of memory doesn't really tell me what the memory speed should be. You say 2800Mhz, which is a very odd speed. Typically 2666, 2933, 3000, 3200. Though 2800Mhz kits certainly exist. 4x8GB kit, not ideal. First thing when troubleshooting, simplify the system, run with a single stick until the system performs as expected.
No mention of storage, shouldn't matter all that much to gaming performance, but if the drive is full, then there might be problems. SATA III or NVMe, I doubt you have enough hardware to run into PCIe lane issues, but how do I know you don't have 12 hard drives and every PCIe slot full...
Power supply is important, if it is undersized the GPU might be throttling.
CPU cooler is rather important, if the temperatures are getting too high, it will throttle. That would something you can check, with core temp or hardware monitor. Check the CPU frequency, is it reaching boost clocks, or is it stuck at a low frequency. Windows often defaults to a low power mode, check power options and set it to maximum performance during testing (switch it back to balanced when you get everything working if you so desire)
You did not answer the question regarding where the monitor is plugged in.
Starting with a damaged system, hard to say what could be wrong.