AFAIK it isn't recommended to have one (virtual shadow maps) without the other (virtualized geometry) ...Not quite sure where to put this - According to this article, the next iteration Assassins Creed / Anvil will sport ray traced GI and virtual geometry. They'd both be particularly good wins for the settings of these games. Hopefully we'll see more not UE engines adopt virtual geometry.
No mension of VSM though, but then the article's quite slight on graphics talk.
EXCLUSIVE - Details on Assassin's Creed Red's Engine, Base Building, Combat, and More
Assassin's Creed Red is the next mainline Assassin's Creed game to release as a part of a new era of the franchise, here's everything we knowinsider-gaming.com
If you want shadows at all with virtualized geometry, regular shadow maps or multi-resolution cascaded shadow maps aren't ideal due to their uniform sampling property which gets very wasteful in terms of work as the resolution increases so other shadowing methods with non-uniform sampling such as SDSM (sample distribution shadow maps) or VSM can skip having to sample parts of the shadow map at full resolution which is the behaviour that we do want when going to higher resolutions ...