Let me put it this way... I'd rank the importance like this:
You were talking about the regrowth from a 3-pop whip, so I thought you meant regrowing all 3 pop. Regrowing 1 pop can happen instantly, but regrowing 3 pop is a serious cost.
- Something you want to finish asap. Granary in new cities, military units for an immediate war, settlers for a good spot, etc (whip a lot, even if it's inefficient)
- Growing small cities bigger, when you have enough happiness and they can work improved tiles (don't whip, maximize food)
- City is mature (using all it's happiness or good tiles). Use mines, cottages, or specialists to use up its food surplus (don't whip)
- You've done that, but the city still has extra food. Whip it, but just a little.
You were talking about the regrowth from a 3-pop whip, so I thought you meant regrowing all 3 pop. Regrowing 1 pop can happen instantly, but regrowing 3 pop is a serious cost.