Yes, they can. Fuzzy Logic contains plotting functions for producing different types of three-dimensional plots of fuzzy relations. There are discrete, surface, and wire frame-type plots. In addition, fuzzy relations can be viewed as membership matrices, which are also supported by Fuzzy Logic. Yes, you can.
Fuzzy Logic contains all of the tools necessary to design a fuzzy logic controller.
Using some of the Fuzzy Logic and Mathematica functions, you can also perform simulations with your fuzzy controller. The package contains a notebook that gives a thorough description of how to perform these simulations. Fuzzy Logic contains a notebook that shows you how to create a fuzzy model of a mathematical function. Step by step the notebook goes through how to create input and output variables, how to design rules, and how to build the model. The model is then tested and compared to the actual mathematical function.