In regards to railroading:
Just remember to plan out situations, not stories. A GM is not an author or a playwright.
So for a traditional Dresden Files game, come up with a bad guy (or bad guys) and a scheme (or schemes). Come up with the groups, figure out some ways they are likely to react. Decide on some clues, i.e., holes in the plan that your players can exploit.
Do NOT come up with solutions, climatic battles, etc. Those should come about organically due to the choices of your players.
Don't worry too much about scaling situations to the players, the world doesn't work like that, and doesn't need to. Sometimes they have to approach situations with a bit more subtlety, creativity or finesse. Other times they will curbstomp their opposition. Both options are fun, as long as they are still given choices, e.g., they aren't just ambushed by a dragon.
As long as you are just presenting situations and allowing your players to interact with the world as they see fit, they will have a difficult time accusing you of railroading.