I've done ferulic and protein rest as well as decoctions. The only difference worth noting was with a protein rest. Doing a protein rest produced a clearer beer once it cold conditioned. It was closer to a kristallweizen, something I don't care for in wheat beers. I like them to be cloudy. The pitch rate and fermentation temperature have the most impact on flavor for my hefeweizens, so I focus most of my attention on those two things. I have one that's about ready to bottle. It's a 5 gallon batch that I pitched from a 1 gallon yeast starter and started fermentation at 62F. I slowly worked it up to 68F over 5 days. It has a nice sweet, spicy, and tart flavor I hadn't accomplished before with this recipe. It's like a mix of bananas, cloves, and granny smith apples. Delicious!. I have also under pitched with just one 3068 smack pack straight into the wort. Even with good temperature control, that one had way too much banana and bubble gum for my taste. But again, for me, step mashes and decoctions have had a negligible impact on taste.