I have a novice's question perhaps some experienced cake decorators can answer. am making a tiered cake and am using 2 inch deep pans. do i need to split and fill the cakes or can I use two cakes with a filling in between? thanks

Either one ... depends on what you like and/or what your client is looking for.

My standard wedding cake is two 2" cakes with icing between them. I've only torted one wedding cake, but I'm starting to do it more and more on shower and smaller cakes.

It's a personal preference. Sometimes I split mine and that will make the tier a little taller. Most often I don't.

It is up to you - there is no hard and fast rule on this. The cake will look more attractive when cut with lots of layers of pretty filling, but it certainly won't be any less stable or anything without it. Scratch cakes tend to need thinner layers and simple syrup to acheive and retain moistness but mix cakes are formulated so that you can do deep layers. Whatever you choose

I also charge more per slice when I torte the cakes.

if you do split the cake how much simple syrup do you use to moisten the cake?