For those saying quantity of RAM doesn't make a difference, that's true to a certain extent, but it can make a fairly big difference especially with Ryzen processors.
Single stick of RAM is always bad these days, all motherboards/processors support at least dual channel, so 2x8GB will perform better than 1x16GB, in the same way 2x16 will work better than 1x16 as the computer will spread the data over the two sticks so it can access them in parellel rather than load it all onto one. (Note much as it might seem like it, no this wont be double the performance

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It gets a little more confusing going from two to four slots with Ryzen processors, as there are configurations in which four slots of RAM will perform better than two slots of RAM (ie 4x8GB will do better than 2x16, or 4x4GB v 2x8GB), and this is tied up with memory ranks, which unfortunately is not something that is generally given as information on the sales information about RAM.
Ryzen (Zen 3) processors work best with 4 ranks of RAM, which is either 4 single rank RAM modules, or 2 dual rank RAM modules. In the past most 16GB modules were dual rank, but with the increasing density of RAM, most are now single rank. The easiest way to tell is to look at the RAM and see if it has chips on both sides of the stick (dual) or on one side of the chip (single), but in most cases to do that you'd need to buy the RAM first (note you cannot go by any pics on most sites, as early versions may be dual rank, but later ones single and the website wont bother to update the pic, or just flat out use a generic pic for an entire range of sizes).
So in the above 4x16 is likely to be better than 2x16 which will be better than 1x16 even if EU4 itself doesn't use that much RAM.