Intel fits its CPUs into buckets for 65 and 95, but that doesn't mean a 95W TDP CPU is actually 95W. It might be 80W or any other number above 65 that keeps it out of that category.
I'm not sure what you're trying to say here. My point was there is no 95 W TDP Comet Lake S listed in Intel's product line. This is a custom binned SKU, probably because their consumer iMac line is not built for 120 W chips (or IMO even 95 W chips for that matter). Dunno about today's 2020 iMacs, but prior to 2020 none of their non-Pro iMacs have used 120 W chips.
The iMac Pro can handle those TDPs just fine, but for whatever reason (cost?) Apple has not chosen to trickle down the iMac Pro's cooling system into the iMac line. Or at least they hadn't for the 2019 models.
In addition, OEMs are free to manage the thermals at a higher or lower level. If they have cooling appropriate for 120W they can allow it to maintain turbo a bit longer, or maybe have more cores at full turbo. If they have less cooling, they can restrict turbo for a shorter time, or have fewer cores hitting full turbo.
I really doubt Apple is going to sell an iMac that sounds like a jet engine when it is under load. Heck, maybe they do something weird and have a heat pipe that uses the entire rear surface of the 27" display to radiate heat, so cooling a 95W CPU is easy.
You are sadly mistaken my friend. The 2019 i9 iMacs are notorious for being loud under load. OK it doesn't sound like a server but it's still pretty loud. I experienced this first hand with the infamous i7-7700K way back in 2017. It was so bad I returned it and bought a much slower i5.
In fact, there are entire threads on music production on how to manage fan noise on the higher end iMacs. One of the solutions these days has been to recommend buying the iMac Pro instead.
I've posted this before but it bears repeating here, given your post above. A bunch of us tested our 2017 iMacs by transcoding a specific video file using identical Handbrake settings. The iMac i7-7700K would ramp up to full loud fan speed within 30 seconds, and then complete the transcode in 10 minutes. My iMac i5-7600 would be nearly silent for most of the transcode, but by about the 9.5 minute mark was at full blast, and then would complete at the 12.5 minute mark. The iMac i5-7600K behaved closer to my i5-7600 despite being a higher TDP class chip. And the iMac i5-7500 just stayed quiet.
The 2019 iMac did not fix this. If anything it got worse, since more than just the top tier model would exhibit this quick fan ramp up behaviour.
The 2020 we don't know yet. We can only hope the brought better cooling to the 2020, but the mere fact that Apple had to get a custom chip SKU for this iMac argues that Apple has not significantly changed the iMac cooling, and they'll probably be just as loud as the 2019 models.
To circle back on the Arm discussion, my belief, or at least hope, is that Apple will rectify this to a large extent on Arm. This is not just a problem with the iMacs, but is a problem with the MacBook Pros too. The high end ones are disturbingly loud under load, according to many reviews.
EDIT:
Maybe I'm biased because I value silence more than I value raw performance, but you get the idea. BTW, I just picked up a 2006 Mac Pro with 2 x 2.66 GHz dual core Xeon 5150 (TDP 65 W x 2) and just for fun have been upgrading it. This thing has massive heatsinks and multiple big fans, which makes sense given some of the chips this design uses. I tested the power utilzation of some of my machines today:
Mac Pro 2 x Xeon 5150: 258 Watts peak during boot, 168 Watts at idle (!), and 37 Watts for the 20" Samsung LCD.
Windows Phenom II 1055T: 126 Watts peak during boot, 85 Watts idle, and 55 Watts for the 24" Dell LCD.
iMac 2010 Core i7-870: 172 Watts peak during boot, 65 Watts idle. Screen is built in.
iMac 2017 Core i5-7600: 94 Watts peak during boot, 38 Watts idle. Screen is built in and has LED backlight.
I'm going to put 2 x quad-core chips in the Mac Pro, but I was debating getting the 120 W TDP 2.66 GHz quad-core Xeon X5355 quickly (Canadian seller), or else the 80 W TDP 2.33 GHz quad-core Xeon E5345 in who knows how long (overseas seller). I ended up going with the latter since many have reported a necessary increase in fan activity with the X5355 chips for obvious reasons.