Soldato
This may be obvious, but can u combine 2x 16GB 4266mhz kits to make 32Gb? They don't have this option available so I wondering if there is a limitation with 32 GB at this speed.
So long as they're the same RAM (and should really be the same versions), yes.
However, generally increasing populated DIMMs will put more stress on the IMC and therefore make it harder to achieve high frequencies. Don't expect 4x8GB DIMMs to achieve beyond 4000MHz.