Every production pays for its VFX decisions either way: early, with clarity, or later, with money and stress. The expensive version is the shot that gets designed in the edit, months after the camera wrapped, when the only currency left is budget.
The cheap version is a conversation in pre-production, where someone senior asks the boring questions before a single frame is shot. What's real, what's CG, where's the camera, what can we get on the day. The answers are nearly free in pre-production and ruinous in post.