No beef with anything offered here so far.
If it's a bit much trying to have your front foot either in the air or on the ground... or on the way to something or other while trying to hit a volley at some height or another, I'll offer this. Think of transferring your weight forward through contact when hitting a volley. Even if your front foot is down on the court, you still want your weight moving forward onto that foot as you hit the ball to help with driving the shot.
For a helpful split step when rushing the net, you might want to think of this as a sort of skip - carry forward momentum into the split step so that you can burst either diagonally forward to the left or the right, or else straight on toward the ball and the net.
The general move through contact for good volleys is more of a side step than a forward move (with shoulders more square to the net). That's why a partial shoulder turn to either side (I like the idea of at least a 45 degree turn) is helpful for the best geometry with that side step through contact. Side step through the volley to drive your weight generally forward toward the net.