the are no regs really on the thickness of the insulation it depends on what U value you want to achieve, usually you would be using around 80 - 100mm, you cant reduce any gaps/passage ways between two houses either under the limit by adding thickness to one house.
the system will be capped off with a soffit profile and it would normally accommodate the gutter above it, or onto it some way but depends on the building and the roof etc.