I think there are two factors in Balefire:

1 - Strength (how far back in time the Pattern is burnt out)

2 - Area (how much the balefire affects - this includes the range of the BF)

I see no reason to believe that Rand moderated his use of the CK. After all, he is taking out one of the top Forsaken, and before this, he spreads the knowledge of Balefire to his Asha'man (Narishma), suggesting that while he knows it is dangerous, he doesn't really realise why or how much it is.

Now, Brandon has commented on how far back in time balefire can take things - we know that at most, it couldn't have taken Graendal back more than a week or so (Brandon said a day or two IIRC), but we know that the balefire was strong enough to remove the Compulsion placed on Ramshalan (probably 20-60 minutes earlier). Note that this minimum is roughly equal to or greater than the amount of time that Rand restored in TFoH with Rahvin.

With Rahvin, Rand used at most 1 metre squared of balefire (likely less, but we'll be generous). We also know that Natrin's Barrow is a large estate, so assuming that Rand's target area was 1km squared is not unreasonable.

1km squared = 1 million metres. This strongly suggests that he is definitely drawing deeply on the Choedan Kal.

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Regarding the destruction of cities in the War of Power, I'd explain it in two parts:

1 - Cities in our world are growing more and more densely populated - AoL cities would have been similar. One square km could hold millions of people in an AoL skyscraper. So there is less area to cover.

2 - We never hear how far back the population was taken. For all we know, the balefire streams were broad but far weaker than Rand's, only taking them back seconds or perhaps even less.