Hey there, just registerd to add my two cents about this topic. Like many others bought this during black friday for a discount and been facing some termal throttling issues.
As has been previously stated, it seems that there's a BIOS policy or sort of misconfiguration that detonates the CPU to get throttled to 400Mhz for short bursts during sustained high demand on both GPU and CPU,which is made worse by the lack of proper ventilation. I undertand that the closed vents may have be done due to the lack of a raise mechanism on this laptop and to prevent dust getting inside but it doesn't improve the situation. I cannot confirm if this happened after a Windows update, but this could also be caused by drivers pushing the hardware more than before or many other reasons.
In any case, I think I've been able to find a sweet spot with some mixed disciplines that in place at the same time prevent the throttling to detonate, keep a decent performance and should allow you to keep your warranty if you decide to keep this hot potato:
Get a cooling pad, I spent 17€ on mine in Amazon.
Set the turbo profile for low demand scenarios in Armoury Crate, or set it to manual and put all the fans all time to min 100%- max100% manually (part of the problem seems to be caused by an underventilation policy so this helps a lot) for high demand games. It's not gonna be quiet but I'm an engineer not a miracle worker.
Open rizen controller and set the temp limit between 62 and 65º depending on your particular setup (even 60º for very dry climates). This should prevent the heavy throttling but you need to keep the laptop cool or the performance will be severely degraded. Experiment with this as will be the key in limit scenarios.
With this configuration and everything in place at the same time (one step missing and you'll be throttled) I've been able to keep a sustained fps unlocked stressing on both peripherals without any throttling for more than 2h of continued execution. Ryzen-controller sometimes gets the configuration lost and must always be enabled the last step. If you make any changes on Armoury Crate you should reapply ryzen-controller settings.
This is not magic and your experience may vary but before repasting or fixing the vents and risking to loose your warranty I thought some may appreciate having a more soft approach. Will keep my fingers crossed for the manufacturer to provide a more elegant fix soon, and good luck with your experiments.