I'm all about that Reddit PCB leak, as well. I'm sure it's been gone over, but I was looking at the leak today and they mention "4 NAND packages soldered to the PCB which are TH58LJT2T24BAEG from Toshiba". Toshiba had those on the XG6 1TB and they are 512GB capacity each, which indicates 2TB(devkit likely 1TB retail?). The interesting part is that whereas in the past a 1GB-to-1TB DRAM to NAND ratio was common, now with the XG6 they included 512MB DRAM buffer. This is reason behind the wording in the leak, "unusual 2GB DRAM per 1 TB NAND". To me that indicates 4GB DRAM in retail 1TB config.
Also mentioned is that the NAND is soldered to the PCB, so no upgradeable SSD/HDD imo. They'll probably allow external storage, but require that you get it onto the 1TB internal drive to play.
As you mentioned there's also the ultra fast Samsung K4ZAF325BM-HC18 GDDR6 memory. That might take slight underclock in retail unit.