I wasn’t very specific at first but a lot of my purchase decisions are around “productivity laptop that can game on the side.”

I wouldn’t say gaming is constrained by GPU memory bandwidth or SSD performance. As long as you have an SSD of any kind, you’re generally fine. Only a few specialized titles like Ratchet and Clank Rift Apart were specifically designed to show off the technical capabilities of fast SSD storage. Most everything else runs just fine without bleeding edge SSD performance, you’re even generally fine running off of a microSD card or SATA III SSD.

Gaming mostly wants to have sufficient GPU RAM capacity and overall 3D rendering performance (for a lack of a precise technical definition of what that means on my part).

Gaming doesn’t tend to move data in and out of VRAM at a particularly fast speed.

Gaming is also generally designed around being able to be released on the latest generation of home consoles, which is now essentially a 6 year old mid-range desktop GPU with 16GB of total system memory.

Gaming is highly constrained by memory bandwidth in the general case. It scales with things like resolution, framerate, and number of textures.

But of course in practice it depends on the details of what you're doing. This is why I acknowledged up front that it depends on what is meant by "really good". I think iGPUs are sufficient for a huge number of titles in the exact same way that an entry level dGPU from 2018 also is. But I don't think most people would consider that "really good" as you'll generally be stuck in the ballpark of 1080@60 and don't even think about photorealistic VR.

I think it's interesting to note that a while back GPU horsepower reached a point similar to that of CPU horsepower and system RAM capacity that's "good enough" for most common tasks. You don't need (and presumable never will) 32 cores or 64 GB of RAM to check your email or watch youtube. Similarly 1080@60 is sufficient to enjoy most game concepts.