Didn't read far enough down the Noctua page but found this that may explain the Ryzen Temperatures:
Copied from Nuctua TR4 website from previous comment:
Attention: Very good case ventilation is recommended for all Ryzen Threadripper based systems regardless of the cooler model being used.
Thermal throttling of the VRM: After some time of prolonged full load, the CPU clock starts to drop off to very low values intermittently, is the cooler insufficient?
This behavior is usually due to overheating of the voltage regulation module (VRM), which provides the CPU with power. To stay within a defined temperature threshold (defined by the component and motherboard vendor) and to cool down the VRM, the clock speed of the CPU might be reduced to very low values. When the temperature of the VRM is back within a safe range, the CPU clocks will be increased back to the expected values until the temperature limit is reached again.
Internal tests at Noctua have shown that not all motherboards on the market are able to power the 250W models at prolonged full CPU load without the VRM running into thermal throttling. In case you experience the behavior described above please, check the VRM temperature (e.g. via HWinfo) and provide additional cooling to this area. In doubt, please contact your motherboard manufacturer for further information.
High CPU temperatures: Even with a high-end cooler, the performance is not what I would expect, what can I do?
First of all, please note that results in reviews might show different results as many tests are conducted in open test bench configurations outside a chassis, which allows a better supply of fresh air and thus allows the coolers reach lower temperatures than in a real-world setup inside a chassis.
Secondly, processors emitting heat-loads of 180-250W or even more (with Precision Boost) create more challenges for case ventilation than lower power mainstream CPUs as it is very difficult to remove so much heat from the chassis. For best performance, it is crucial that sufficient amounts of fresh air can enter the chassis and that warm air leaves the chassis as fast as possible.
Internal testing at Noctua has shown that many PC cases are rather restrictive when it comes to air intake and exhaust due to dampening materials, doors, covers or a rather closed design approach in general. Increasing the number of system fans can help to a certain degree but will not provide much improvement if intakes and outlets are too resistive. The best cooling results are to be expected from cases which use a rather open approach (e.g. mesh walls and intakes). Unfortunately, Noctua cannot provide detailed recommendations for individual system configurations as there are too many options and variables available to give general recommendations. Please refer to general case cooling guidelines such as this one for information how to setup the airflow inside your case.
