Bands (comps and bonuses) vary by line of business. Example, a Band 6 in Legal could make more than a Band 5 on an Administrative Team. The lower the Band Level, the more senior you are in management.
Generally, Band 5 is when you become bonus eligible and entry-level management or something specialized, like an analyst with no direct reports. Band 5 is when you can receive an AVP or VP title as well.
Don't know about Wells Fargo's structure so can't provide input on that but hopefully this is helpful.