Luggage allowance on trip w/ mixed fare classes

I wasn't able to find an answer to this question and I was hoping to get a quick feedback while raising the visibility in case someone else will have the same question.

What is the luggage allowance on a international trip with multiple stops and with different fare classes?
In my particular case initiating leg is Economy (Y), Business (C) <--longest leg, Business (C) again. Return is the same but reverse with the last leg in Economy.
Is there any difference in case of miles award ticket?

Thanks for the replies!