Alienware Aurora Ryzen Edition Trouble

Although that Ryzen 3000-series CPU had decent single-core performance (albeit only mediocre when compared to newer-gen CPUs), the bigger problem is overheating. You see, that Alienware PC, simply put, has a poorly designed chassis to begin with. It is designed to use only a single 80 mm cooling fan, which is woefully inadequate by modern PC cooling standards. Worse, most of its components, including the system's motherboard, are very proprietary, and cannot be upgraded at all with better-performance motherboards and coolers. In fact, your PC's clock speed might have throttled down to an extremely low clock speed even with a light load.

And what made this worst is that AE is almost completely single-threaded outside of certain features.

Put them both together and you've simply bought the wrong overall PC package for anything that comes even remotely close to video editing. That PC has a funky looking case that's extremely poor at airflow.

And the reason why your MacBook Pro performed about equally to your desktop is that like your desktop, that MacBook Pro ran too hot for the CPU it contained, throttling it's clock speed way down under normal use conditions.

>RTX 2080

Do not count on Windows to be fully up to date when it comes to device drivers
Go to the vendor site to be sure you have an updated driver for your graphic adapter
nVidia Driver Downloads https://www.nvidia.com/Download/index.aspx?lang=en-us
-for all Adobe programs use the STUDIO driver, not the GAMING driver
-To achieve the highest level of reliability, Studio Drivers undergo extensive
-testing against multi-app creator workflows and multiple revisions of the top
-creative applications from Adobe to Autodesk and beyond
If you have a laptop you MAY also need to check for a laptop specific nVidia driver
-SOME laptops require an approved driver from the laptop company, not nVidia

There are also intermittent reports that the newest driver is not always the best driver
due to driver bugs or compatibility issues, so you MAY need to try an earlier driver version
This is about Premiere Pro, but the nvidia driver is the same for Premiere Elements
As noted in https://community.adobe.com/t5/premiere-pro-discussions/bad-performance-with-high-end-gpu/td-p/13456115
First, the last Nvidia driver that is known stable and usable at this time is the 517.40 Studio
driver. The later ones have been a mess for many users even in Resolve. So ... go to their site,
the 'older drivers' list, and do a clean install. That may help some.