Artificial Neural Network Guide

Hello mathwork world, I am currently an undergraduate conducting research regarding Artificial Neural Networks, specifically I am trying to estimate AASHTO Based Load Ratings for Composite Steel Girder Bridges using Artificial Neural Networks. I have only been using ANNs in matlab for about three weeks now and have a couple questions. 1. Matlab gives you the option of using ANNs in nntool, nftool, and with commands. For prediction purposes which one of those three is best? 2. If using nntool, what training parameters should be changed according to my dataset? and is there any way of changing the weights by using logic? 3. I have read several published papers and have navigated through forums and either users are extremely proficient or it seems one knows just enough to get through. For accurate estimations for my research would anyone suggest just knowing enough or would someone need to be proficient to be able to use ANNs? Thank you.