LPDDR4X V wbt reram siox, page-10

WBT's ReRAM 100X to 1000X faster than flash, approaches DRAM speeds. 

So definitely a massive improvement over ssd/flash/usb drives etc. 

Replacing DRAM is not really feasible as the write cycle limitation would mean the system would become faulty as soon as the the write cycles lifetime is reached. In a traditional computer random access on the storage is avoided during application execution, but working information is swapped from hdisk to RAM for manipulation as this is much quicker. As a previous poster said, at the very least using ReRam instead of ssd would still result in serious improvements because the swap file would be running off a medium that is a lot faster. Think 100x to 1000x times the speed improvement using an ssd gives you.