I'm ready to return this Ryzen stuff and just buy a 7700k, I'm so goddamn sick of the fans being at full speed while web browsing. What the hell is wrong with this stuff.
I'm not familiar with Noctua really so I went to the site. http://noctua.at/en/nh-u12s
http://noctua.at/media/blfa_files/infosheet/noctua_nh_u12s_datasheet_en.pdf
That one shows a max fan speed of 1500 rpm, and they talk about some Low-Noise Adaptor that can drop that to 1200 rpm.
I don't see how that would be very loud, even at full speed, especially with that adaptor.
You mentioned 2 Fractal Venturi fans. I checked the specs for those and found this: https://www.newegg.com/Product/Product.aspx?Item=N82E16835352022
Those are 1800 rpm fans, so yes, I can understand those will be pretty loud at full speed.
I would go back to the stock Noctua fans. They should cool well even if they run full blast, and if you use the adaptor that would drop the noise even more.
As others said you are really 20 C lower that what you think, so 75 in games is really 55 which is nothing. No problem there at all. Slower fans won't hurt much because it's such a good cooler to start with.
A fan change will take care of the issue.