Some gutter guards work better than others. The design of the roof, size of debris (pine needles, leaves, seeds) and gutter guard material quality all determine the product best for the house. A poor design and neglected maintenance can contribute to ice damage.
The distance between the bottom shingle and the top of the gutter is an important factor in choosing a gutter guard. If an installed gutter guard is level, snow and ice may force water behind the gutter and fascia.
If the high end of your gutter is jammed up so it touches the shingles you may need to see if you can lower the pitch and still have it drain properly. Then the gutter guard will have some slope so debris will wash off during a rain.
Before you purchase a system for your whole house, get a section and try it at several locations around your home. If there is sufficient pitch you can go ahead and install the whole house.
Gutter guards are available in many styles and qualities. Here are a few:
Screen or wire mesh in a roll. Cheapest.
Rigid plastic and aluminum with holes or slots are stiffer than rolled but can trap pine needles and the whirly things from maple trees. Cheap.
Rigid plastic or aluminum with one or two louvers that let debris slide over but capture most of the water. Good.
Rolled mesh gutter guards are probably too weak for your situation. It comes in a twenty-foot roll. The problem is that in the winter, snow and ice-dams crush the material down into the gutter.
Next, there is a rigid mesh gutter guard. It is like the rolled material but much stiffer. It is better than the rolled guard but still lets small debris in to the gutter.
Stronger yet is a rigid PVC gutter guard that is flat with holes. Some have ribs for greater strength. This style comes in four and eight foot sections. It is not unlike the mesh guards in that it strains the water but still lets small debris through. This style is effective on steep roofs where debris will not pile on top of the guard.
Last is the louvered gutter guard that allows water to roll in a vent, but lets debris slide across to the ground. This style comes in four and eight foot sections.
Whichever product you chose, proper installation is as important as the product. When the gutters are up to the bottom of the shingle, the gutter guard will lay too flat. To remedy this situation you will have to lower the entire gutter section so the gutter guard will be pitched at a proper angle.