I'd never used the buttercream before, so I kind of wanted to throw it in the mix. I'm honestly not sure what buttercream tastes like. I think I just saw that it was commonly used with Angel Cake so I added it.
It's worth a shot. I only have experience with the Angel Food and the Tahitian Cream. I think those two will pair nicely for those fruits you are adding.
I always mix my first mixes at 10mls, then if they are good I'll do a 30ml (remember I mainly subohm) to see how it ages/steeps past 3 weeks... If it ages well then I mix larger batches.