So I'm not an expert, I'm actually learning a lot about this stuff as I built my latest PC with cooling in mind this past September. However, I have the same processor and CLC as you, so I think I can offer a good comparison and hopefully answers.
 
I also have an i7-9700k, clocked to 4.6-4.8 GHz, and I've always ran it with the same CLC as you. I live in Arizona, so right now it's in the low 90's outside, and inside the room I'm in it's 78-80 degrees Fahrenheit (AC is expensive, especially during the day). So I'm not in the most optimal environment for a cool PC, but I still get pretty good results with my build. I have the CLC positioned at the front of my case as an intake, taking air in from the front panel and into my case. However, I have two Noctua Chromax NF-F12 fans pushing air through my radiator instead of the stock EVGA fans, but in my small amount of comparing, it didn't make much of a temperature difference (though they're certainly quieter).
 
My processor idles at 32-34 degrees Celsius, depending on the ambient temperature. During the winter, when it would be half the temperatures outside at night as it is right now, and I left the windows open to the room overnight, I got much cooler temperatures than that. But generally, my processor rarely goes beyond 50 degrees Celsius. The games that have hammered it the most have been Star Wars: Battlefront II and Battlefield V (Frostbite loves to hammer the CPU it seems). I used to get temperatures between 55-60 with those games, but that was because my case's front panel didn't have great airflow. When I took off the front panel, the temperatures would go down considerably, down to 50 give or take. I got a front panel that's a mesh now and has much better airflow, and get the same results.
 
I just played about half a round of Battlefield 4 64 player Conquest on Giants of Karelia, all settings on High or above, running at a stable 1440p and 144 fps, and my temperatures were stable at a range of 44-48 degrees Celsius, which is typical for my system, as I said above. So my results are about 20 degrees cooler than yours, despite having the same CLC and processor, playing the same game at rather demanding settings.
 
What case and GPU are you using? Those two components can have an effect on your CPU performance/temps. The case obviously for airflow or radiator placement, but something I just learned in a JayzTwoCents video recently where he talked about how "streaming PC's" are unnecessary, as you can get good results with relatively low-level or budget parts, is that the more work you offload to the graphics card, the less work that's being demanded of the CPU. E.g., turning game settings up to high will put more demand on the GPU, reduce the amount of frames being rendered, and thus reduce the workload of the CPU, decreasing its temperatures as well. So if you have an underpowered GPU, or are playing on low graphics settings and getting super crazy framerates, that can have an effect as well.

EpicSurvivor
Thanks for your reply. That's insane! I don't understand how there can be such a gap difference in temperatures. I have the MasterCase Pro 5. What voltage do you use for your overclock and what Motherboard are you using?

My motherboard is an MSI MPG Z390 Gaming Plus. I don't know for sure the voltage, since the overclock seems to be automatic through Intel's Turbo Boost Max Technology (it's enabled by default, and I never set any specific overclock settings). My motherboard BIOS says that it's at 3.6 GHz and 1.0 volts, but when I boot Windows, it automatically goes to 4.6-4.8 (though knowing exactly what clock it is isn't clear; RivaTuner shows a locked 4600 MHz on all cores every time, but HWMonitor shows fluctuating speeds from anywhere between 800 MHz to 4800 MHz on different cores). I've never touched any BIOS settings for processor speeds, but I have enabled XMP for my RAM. According to HWMonitor, my processor is running at generally 1.160 volts.
 
Again, I'm not an expert, I'm learning some of this stuff as I go. I just put the computer together and it's been automatically overclocking my processor for me, and I just shrugged.
 
That case looks like it would have decent airflow. Where do you have your radiator positioned, and how do you have the fans configured?
 
In addition, what are your idle temperatures, and how are you getting to 67 degrees? Is it a steady rise and then it peaks out around there, or does it jump up there more rapidly?