The Leeds Method is very valuable in sorting out grandparent lines from DNA matches. Unfortunately, one of my lines has no matches with whom I share 90-400 cM. Thankfully, a brother has tested and he does have one of that line in that category. This is one of the values of having siblings tested, as we match with others in some cases quite differently, but the earliest generation in your family that can be tested the better. For all you want to know on the Leeds method, see
The Leeds Method of Clustering DNA Matches – Dana Leeds
The Leeds Method helps adoptees and genealogists to sort their DNA matches into clusters helping them to identify their cousins and shared ancestors.