I don’t think it’ll be a huge jump in performance or anything, but maybe a bit. It’s not likely that you’ll see the kind of performance gain using a dynamic directional light with shadow casting enabled vs disabled. I think this feature request at least provides more artistic control over the landscapes used though.
As for dynamically lit worlds, keeping the CSM shadow distance to a minimum and using Distance Fields for further distances (like Kite Demo) is the way to go. Dynamic lighting in general is expensive due to CSM taking into account each triangle no matter the screen size, which is why it’s expensive.