With any wide foot the first thing you need to do is get the footbeds correct. Often a wide foot is actually a pronated foot. This inward leaning of the foot makes the foot appear wider then it actually is. Without first supporting the foot from beneath you can not work out what will be an appropriate width shell.
A goo fitter will look at the support of your foot and take this into account when shell checking. He may then make footbeds before trying boots depending on your stability.
If non of this makes sense dont worry, that is the reason boot fitters exist. They do all the hard work and you end up with good boots, if they know what they are doing. Which is the moat important part. Dont bother researching boots. Research who the best fitters around you are.