A copy of the dev blog without the images : https://fasrtraveler696.weebly.com/blog/dual-universe-trailers
edit:
NQ uses Unigine to process the voxels procedurally generated, there is no bigger dataset for bigger planet, at least for the core terrain.
The additionnal data for voxels are all additions that NQ did on top of the core generation (here is a video about their editor), and all players modifications to the terrain. Add to that all the constructs with elements. All of that is stored on the RAM, the more you have the more detailed the world is.
To faster this process, the game client stores data locally in a cache folder. It checks for deletions or additions of the voxels with the server and avoid redownloading every voxels data for the place where the player is.
As DU is not a single player game, all of this data must be synchronized between players, but not only voxels. All positions and orientations of constructs, all elements states (broken elements, lights, engines, force fields, etc), must be known to be correctly displayed and in sync with each player.
The CPU generates optimized meshes with the desired LOD for the terrain and constructs, then the relevent data is sent to the GPU to display everything. As said above, the culling is done on the GPU instead of the CPU.
I might be not right on all aspects of the game, but at the end, it needs so much hardware to work decently that I'm concerned by the targeted player base. Not everyone can run this game decently. Add to that the niche game design, at a time where fortnite and short game sessions and fast consumption of games dominate the gaming. But the potential of DU is immence, so believe in it
To speak of NQ as a compagny where not every employees are devs, I wouldn't compare a prototype voxel engine (as good as it is) or other voxel experiments to a functionning (as far as it is) multiplayer game, with an immence single shard world and all of its new techs (client and server).