To me, the very important information is that you are a very competitive fps player.
I am not one, but I do a lot of reading, and in my previous life I was a performance specialist.
On a gross level, your cpu and cpu performance are the main determinants of performance.
Games will differ in how they use the cpu.
Try the test mentioned above and see how you do by reducing the gpu load on YOUR games.
If you get an FPS improvement, it suggests that a stronger graphics card would do you some good.
Likely, a 3080 is not what you want if you are playing at 1080P and perhaps not even at 1440P.
Wait and see what a 3070 brings. Or, you might find that a GTX1080ti will do the job; they should start to be discounted.
Have you overclocked your I7-4790K?
If not, you are leaving some 20-30% performance on the table.
Here is another experiment to try:
Limit your cpu, either by reducing the OC, or, in windows power management, limit the maximum cpu% to something like 70%.
Go to control panel/power options/change plan settings/change advanced power settings/processor power management/maximum processor state/
This will simulate what a lack of cpu power will do.
Conversely what a 30% improvement in core speed might do.
I suspect that a change to a 10th gen K suffix processor would be that last step up in cpu performance for you.
What you are looking for is an OC or turbo for the top two cores to go past 5.0
The i5./7/i9 K processors will all do that. The main difference is how many threads you get.
12/16/20 respectively. The ryzens are attractive, but the best they can do is around 4.3.
To see how important the number of threads is to your games, here is another experiment to try:
You should also experiment with removing one thread. You can do this in the windows msconfig boot advanced options option.
You will need to reboot for the change to take effect. Set the number of threads to less than you have.
This will tell you how sensitive your games are to the benefits of many threads.
If you see little difference, your game does not need all the threads you have.
Only in multiplayer would I expect to see much benefit past 6 threads.
I think a i5-10600K would be very good. I7-10700K at most. You will want a Z490 based motherboard.
Here is a review:
https://www.tomshardware.com/reviews/intel-core-i5-10600k-cpu-review/5
Your ram is not the fastest, but Intel does not need fast ram for performance.
It will do.
Gaming on a HDD is not best. Why is that?
Aside from level loads, a game must load graphics textures from the game drive and do game checkpoints.
That is some 40x slower on a HDD compared to a SSD.
A 1tb SSD is not that expensive. Without changing the motherboard, try a samsung 860 evo.
If you have a z490 based motherboard, pay a bit extra for a m.2 pcie ssd like the samsung 970 evo plus.
You will need ddr4 ram. A 2 x 8gb kit in 3200-3600 speed is fine.
What is your mouse and mouse connection?
If I am not mistaken a wired ps2 connection is a bit better for gaming.
I can't talk about mice, but that could also be a factor.
Mice are cheap if you can identify a mouse upgrade.
What is your monitor?
Yes, refresh rate is important. But there is also the issue of input latency that can be helped with buffering.
Here is an older article that might be relevant to you:
https://www.anandtech.com/show/10325/the-nvidia-geforce-gtx-1080-and-1070-founders-edition-review/13