The custom AMD chip inside the 15-inch Surface Laptop 3 is an all-in-one chip that includes a regular processor as well as a lightweight graphics chip for lighter graphical workloads.
It may not be enough for a discerning professional — which is where an external GPU supported by Thunderbolt 3 would be great. At the same time, even though it's lightweight, it's actually more than most people need, at least those who typically run regular apps like web browsers, chat apps, and things like Microsoft Office.
Still, being all-in-one, it doesn't necessarily add to the heft and size of the laptop. It affords a more portable design.
The Surface Laptop 3 I've been using is the $1,700 mid-range model that runs on the AMD Ryzen 5 3580U and 16GB of RAM. For my workload, including lots of tabs in Chrome, Slack, and the occasional lightweight Photoshopping, the Surface Pro 3 has performed admirably.
It's true that you can get a cheaper 15-inch laptop with similar performance in the base-line $1,050 Dell XPS 15 that comes with an Intel Core i5, and even better performance in the $1,350 that comes with an incredibly powerful Core i7 and an Nvidia graphics chip. In fact, the Surface Laptop 3 is technically poor value compared to the XPS 15 if you're comparing specs.
But then again, the Surface Laptop 3 is thinner, lighter, and more portable, while the XPS 15 feels more like something you should keep on a desk rather than carry around.