Yes, you can do that, but increasing the radius too much will hurt performance. It’s still better than before, as they’ve made significant performance improvements for ray tracing in 5.4+. Also, keep in mind that these commands will also impact RT Reflection and HWRT Lumen.
In my tests, even with a larger culling radius and LODs, it still doesn’t match the VSM distance with Nanite. And like you mentioned, the shadow tends to pop in at a distance.
I tested this a few months ago, and it doesn’t work that way. It will still be calculated. It’s similar to a light source with low intensity, you won’t see it, but it will still calculate the shadow it casts. This is actually why they implemented the “World Position Offset Disable Distance” for each actor.