If you don’t need a large amount of RAM and want to save money, it’s probably better to go with 2 smaller sticks, i.e. 2 X 8 GB, rather than 1 X 16 GB, in order to take advantage of dual-channel RAM.
Maybe it doesn’t normally make a difference, but it’s enough of a difference here that the GPU is starved of memory bandwidth enough that it can’t manage an external display:
If this isn’t an issue for you, you can go with 1 X 16 GB and if it does become an issue, just add a second 16 GB stick.