To oversimplify, there are two types of solutions: ideal ones and practical ones. If your children fight frequently, the ideal solution is to teach them to get along better. This is often quite difficult to accomplish. Some practical solutions are to separate them (just yesterday I recommended separate bedrooms for two siblings) or pay them for getting along. It doesn’t feel right to most of us to pay our children to treat each other appropriately, but sometimes even this technique can help reduce family stress and break the pattern.
It is important to remember that one size does not fit all for ADHD. Some children, if you let them run around a great deal prior to bed, will settle down and go to sleep. Other children might become over stimulated. The goal is to when in doubt try something. If it works, great. If it doesn’t, alter your plan or try something else.