I wish I could help. I am up to 30% on some of the flavours and dabbling with both ethyl maltol and sweetener. They need a little more steeping, but are now showing some promise - some of the fruit ones are beginning to taste like they should.
I had a convo with my mate who's nickname is Cakey and she said they are well thought of in the baking world. Of course in the baking world loads of sugars and sweeteners are added - and in differing types and amounts according to recipe and use (e.g as a main flavour, background flavour or for an icing or butter) there'd also be no EM used as this wouldn't be either necessary or useful. It was helpful.
So I can see myself ending up with some vapes that may have 30% flavouring and a mix of an additional 10% split over ethyl maltol and sweetener. Normally at these sort of levels I would give up and seek something else. However, the value proposition of Cupcake World at 30% use is still very. very good, so I am persevering. I need to (in my little head) be able to mix up a flavour straight to its best, before I start mixing with it - that way, my little head understands it.