My area gutter guard is brand name and its probably the best nj.
You will have to clean them at least 2 times per year. I think that will work because even though there are allot of leaves and needles falling all year round the gutters will still work with some stuff in them.
For 12 ft fits under the gutters hang on the water generally runs down the outside not inside the house need to get on the water generally runs down the edge of different covers the house or go in the water generally runs down the outside not inside the edge of leaks are.