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CPU Wattage & Heat Issues i9-9900k (95W) vs i5-8500 (65W)

Level 7

First off let me say I've built a few pc's but by all means not as advanced as most on this forum, my weakness is understanding the wattage & capabilities between cpu's & gpu's along with Bios. I can take my experience just so far so that's why I'm reaching out.

I did a itx build with spare parts, no gpu, & not for gaming, it's used for light office work & web surfing. I have an ASUS Z390i paired with an i9-9900k (95W), cooled by be quiet Pure Rock LP 100W TDP air cooler & want to change the cpu to a i5-8500 (65W). The Bios is compatible with both, checked that on ASUS web page. 

My temps are 30C at idle & when in use fluctuate to mid to high 30's hitting 40's at times then 50C once in awhile depending on cpu usage. At rest its back to 30C to 35C with a few windows tabs open. This is well within safe operating limits.  

Herein lies my question; If the i9-9900K has a TDP of 95W and is known to be a hot cpu & the i5-8500 has a lower TDP of 65W, would the temps be identical with the same usage? In short for example, if I'm watching a video on YT, and have a few tabs open to other web pages & temps on the i9 is at 38C with fluctuations upwards to mid 40's would it be the same identical temp readings on the i5-8500? Would there be any benefit to changing out the i9 for lower temps? 

I have no room for anything but a low profile cooler, the case is a OSMI 3.0, if you're at all familiar is quite tight inside. All is working just fine but the i9-9900k is overkill & could use it later down the road, but if the i5-8500 will provide lower temps with the same usage as mentioned above then I would purchase it. The be quiet Pure Rock LP cooler is fairly quiet, but even with a custom fan curve you can still hear the fans rev up when taxing the cpu. If the i5-8500 provides lower temps then the Pure Rock would be really silent, & that's my goal. 

Since the i9 is a hot cpu in general (95w) with 8 Cores & the i5 (65W) has 6 Cores I'm thinking that the i5 would provide better overall performance because I'm making better usage of the cores more then I would with the i9. Plus the wattage is lower (65W) cooler running cpu overall.

I realize that the TDP's are at full capacity, I matched the i9 with a 100W cooler, works fine but looking for it to be quieter for office environment.   

Thanks for reading & your thoughts on this.