Before using heavy tools shoiluld I make sure room temps ok. Windows open lol.
Also I was looking into cpu upgrade amd 75xx nxt one up but needs new motherboard new ram which is big no.
I just bought a 4090 and asked the same question. Superposition is good. It utilized 99% of my GPU. My temps stayed really good with my MSI Gaming X Trio.
What you should do is make 100% sure your power cables are connected appropriately. My card came with an adapter to go from the GPU to 3 8 pin connectors. I used PCI-E cables that came with my Seasonic PSU. They were 6+2 pin on the PCI-E end but only 6 out of 8 pins on the PSU end. I ended up emailing Seasonic to ask if this was an appropriate way to connect a 450W GPU and they said yes. Also make sure you have a 850W minimum PSU.
There are a large number of posts stating that the 4090 can be power limited with little if no performance loss. I used Afterburner to set the power limit to 80% which should be around 360W. I am monitoring all the time with HWinfo. My GPU is indeed now only drawing 360W max.
The presets for Superposition skip over 2K but you can hit the drop down box to select that or other resolutions. I even ran a test with the 8K setting.
I also ran Superposition before I limited the power to 80% with no issues. If it runs ok at 100%, 80% power limit pretty much ensures that you should be stable.
As for upgrades, the best gaming CPU for your MB is 5800X3D. I have a 5900X and from what I have read the improvement is minimal. Your 5950X should be fine until you upgrade to AM5 platform.
I have started looking into the AM5 platform myself. I have been eyeballing the 9900X and wondering if they are going to release an X3D version. For right now I am not upgrading. I have too many high end parts that are only about 3 years old to upgrade right now.
One other thing to mention is that some GPU's come with a dual BIOS. One for silent (fans off until preset temp) and one for gaming. I would highly recommend not setting it to silent. It allows the GPU to heat up quite a bit and then it is harder to cool it down again when under heavy load. My 4090 runs extremely cool. Way cooler than my 3080. Everything I have read says they way overdid the cooling on the 4090's which is fine with me.
I would highly recommend MSI Afterburner. It works with any GPU. You can set a custom fan curve. I have mine set to run the fans at a minimum of 30%. It gradually ramps up to 100% fan speed at the thermal limit. You can also set an on screen display for things like CPU temp, GPU temp, FPS, etc. There is also the option to display these settings in your taskbar if you want so you can monitor temps all the time.