ALooking for some tips from someone who's made these before. I want the cupcakes to have a slight dome but not too much. I'd also like the cupcakes to be domed when they come out of the oven so I don't have to build the dome with frosting (don't want it to be squishy underneath the fondant). How much batter should I fill each liner with to ensure good size cupcakes for this project?

AExperiment. We can't answer you because all recipes are different, ovens are different, muffin pans/papers differ. There are just too many variables for anyone here to answer.

You need to your own R&D.