S.T.A.L.K.E.R.'s Dynamic lighting maybe resource hungry: but I have no huge FPS problems with it ^^. Must be a good engine.
I don't know anything about it.
Single light or "few light" dynamic shadows are doable in a couple different ways. Mythruna has an "infinite number of lights" system which makes shadows harder. I could potentially do dynamic shadows for only the sun and moon but then I believe it would make the other lighting feel overly bland in comparison.
Eventually there will be player carried lights and it will be weird if the sun casts long shadows and they don't.