I found a benchmark article today that showed that AMD chips (and Intel, to a lesser degree) have a significant performance bottleneck with single-channel RAM and integrated graphics (i.e. no graphics card). Upgrading to dual-channel RAM gives about a 75% performance increase for AMD, 25% for intel.
"single channel RAM" means only 1 stick of RAM. "dual channel RAM" means 2 paired sticks of RAM. The theory here is that a single channel creates a bottleneck for the CPU vs the integrated/onboard GPU when gaming since they must use the same RAM.
I also see AMD Ryzen benchmarks showing a 30-50% performance increase even WITH a video card. However also not sure RetroArch is intensive enough for this to make a difference...
But if buying a new laptop, especially without a video card, I think it makes sense to make sure to get dual channel RAM since it shouldn't cost much more.
How to find out if you have single- or dual-channel RAM (without opening up your computer case). You can probably upgrade for ~$40-$50