Finally my experience with the portal was:
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I did the first 3 missions (normal, hard and insane) and got 45 tokens and more than 100,000 coins.
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From there I did 10 or 15 more missions in insane mode and each of them gave me 9,650 coins, except 2 that gave me a little more than 28,000 coins.
Conclusion: BB insane mode gives more coins. And … it seems to me that there was a bug or something that was not right.