Unplayable gaming build with high CPU temps

[Fancy-Toast]

Operating System: Windows 10 64 Bit
MSI MPG Z390 GAMING EDGE AC ATX LGA1151 Motherboard
Intel(R) Core(TM) I9-9900K cup @ 3.60GHz
Gigabyte GeForce RTX 2080 8 GB WINDFORCE
RAM 16 GB

ARCTIC Liquid Freezer II 280 72.8 CFM Liquid CPU Cooler
Bios: A.B0
All other drivers and windows updates are current.  I'll add a link to my current build.  Sorry, there aren't any pictures uploaded yet.

 

https://pcpartpicker.com/b/9F3tt6

 

This is still a fairly new computer built in May of 2019, as of August of 2020 I upgraded to a new case with better airflow and upgrade my heatsink because the one I had before wasn't cutting it.  I started having CPU overheating issues in June 2020.  I haven't been able to determine what has caused the CPU to continually overheat.  After the first go-around with the new case and heatsink, I was still getting temps easily hitting 100 °c with a 10% or less CPU load.  We're talking within minutes of running Red Dead Redemption on the LOWEST settings.  Idle temps were in the 60 °c - 70 °c.  In September I had a tech come over and take a look, he came highly recommended by many of the people in town and some personal friends of mine.  Did some updates, removed and re-applied thermal paste again, did a clean install of windows, and the idle temps dropped down to a happy 30 °c - 45 °c.
However, the issue still wasn't resolved as I continued to see ridiculously high temps when running all sorts of games, Planet Zoo, The Isle, Red Dead Redemption 2, Jurassic Park Evolution, and all on low settings I'm still hitting 90°c even up to 100°c.  I do not seem to have this issue with some other games such as Among us, or Final Fantasy XIV Online even during large raids with all graphics and effects as high as they can go.  Additionally, my GPU temps have never been an issue, I think at one point the highest I saw them was 80°c before it dropped down in the 70s
I am at an utter loss, the Tech couldn't even figure it out.  I'm still new to all this computer building stuff as all the major components are from my very first build, the only thing that's changed since then is the case and heatsink.
Is it possible it's a bottlenecking issue?  Is it possible my CPU can't keep up?  Though isn't that a little strange for an i9?  Or have I overestimated its ability to handle what I throw at it?  Or am I just SOL and have a crap build?  If anyone has any idea please please please give me suggestions, a lot of the stuff I thought my system could handle with ease are unplayable for me.  Also, please be patient and try to explain it like you're talking to a person new to the gaming computer world, because well I sorta am.

[Hold-Ma-Beer]

Well, I dont think you have mentioned about the cooler you're using anywhere.

[Fancy-Toast]

9 minutes ago, Hold-Ma-Beer said:

Well, I dont think you have mentioned about the cooler you're using anywhere.

Sorry I thought I had added it in the description but I guess not  I've added it now, thank you for pointing that out!
The cooler I'm currently using is an ARCTIC Liquid Freezer II 280 72.8 CFM Liquid CPU Cooler

[Hold-Ma-Beer]

Assuming you've not done any OC, your AIO might be faulty. Can you see whether the pump is working through software?

[Fancy-Toast]

21 minutes ago, Hold-Ma-Beer said:

Assuming you've not done any OC, your AIO might be faulty. Can you see whether the pump is working through software?

It seems to be working based on this reading, unless I'm looking at something wrong  fans are spinning, and when the CPU temps jump I can feel heat being exhausted from my computer.  I have the radiator installed on the top of my case rather than the front or back.  CPU temps are fine here but that's because I'm not running anything right now.
 

[Fancy-Toast]

Adding to this if anyone is able to answer this conundrum, is it possible my CPU is receiving too much voltage?  Would undervolting the CPU be a possible option?  I read something about it, but am looking for advice before I do anything.

[Hold-Ma-Beer]

9 hours ago, Fancy-Toast said:

Adding to this if anyone is able to answer this conundrum, is it possible my CPU is receiving too much voltage?  Would undervolting the CPU be a possible option?  I read something about it, but am looking for advice before I do anything.

Unless you've played with the voltage for overclocking, it shoud not be an issue [ If its stock ]

[Fancy-Toast]

47 minutes ago, Hold-Ma-Beer said:

Unless you've played with the voltage for overclocking, it shoud not be an issue [ If its stock ]

No I never have, I did a bunch of research and dove into some further troubleshooting throughout the day today.  Did my regular de-dusting two weeks earlier than I normally do, and may have found a fix.  Running some tests to see how it's handling what I throw at it.  If it's worked I'll be sure to post a solution update here

[Fancy-Toast]

Turns out the issue wasn't the voltage and I didn't need to turn this down, I had to go into BIOS and turn off CPU boost instead!  I don't know how it was turned on in the first place, but everything is playable again!  The highest my CPU temperature went tonight after running multiple tests on multiple games was 65°c!  I don't know how CPU boost was turned on in the first place, but I assume that prior to June it wasn't on.

[Hold-Ma-Beer]

23 hours ago, Fancy-Toast said:

Turns out the issue wasn't the voltage and I didn't need to turn this down, I had to go into BIOS and turn off CPU boost instead!  I don't know how it was turned on in the first place, but everything is playable again!  The highest my CPU temperature went tonight after running multiple tests on multiple games was 65°c!  I don't know how CPU boost was turned on in the first place, but I assume that prior to June it wasn't on.

What does CPU boost even do O_o