It is only dual channel anyways, so they would perform the same. So i would do 2x16, that way you can add extras later on.
But make sure to get the right speeds:
It supports up to 2 SODIMMs of DDR4-2666 RAM, or up to 4 DDR4-2400 sticks.
as mentioned above, we’d need to operate at 2400 MHz to support all four slots—but at least upgrades are relatively simple should users find themselves motivated.