I haven't been able to find basic info on the different classes?

Simple stuff like what armor for which as I'm struggling to understand which to choose as quest rewards. (if only they were marked 'light/medium/heavy' or 'plate/leather/cloth' or something).

Although I know changing class is possible at some point is there any restriction on what other classes are available depending on starting class? (I have 2 characters atm and trying to decide between them)

Also any tips that you wish you had known when you started? Thanks