I am a bit confused on the memory. How are they shoving 128GB into a 4 slot dual channel system when the best desktop DIMM size is 16GB (unless we count the 32GB Samsung ECC memory that can't be used here). The max you can put into a non X299 system is 64GB. Even SODIMM is still limited to 16GB DIMMS.
After doing some research it looks like Samsung does have a 32GB SODIMM module but I cannot buy it anywhere yet so I guess Z390 and the new i9 will be when full support launches for it.