What I can say from my experience is that something like snow where i just futzed with the basecolor, pbr, on a 2k landscape w/1megatexel (14,1,2) RVT, it would update realtime on the whole thing bit in slightly under a second. You could see all the tiles flicker/update rapidly. For smaller things, it should work better but I have yet to test. I was trying for worst case scenario there in being zoomed out looking at the entire thing. If you are in a valley or likely only to see a subset of landscape tiles, it would seem to be ok.
You can also do stuff after the sample from the VT. That will work in real-time as it’s not something in the VT itself, but on-top/after. Generally, I find, keep the VT static, but you can trade that for upping the res/detail given you can also enable streaming.