At some point there will be fish throughout the entire river so the where really depends on when you plan to go. Early in the season (like now) the douglaston is where you probably want to be . As the season progresses there will always be fish trickling through there but upriver can have higher concentrations of fish whereas the lower river will have fresher fish. As the season progresses certain areas will have worse crowding and the douglaston does limit the number of rods. When to go is also largely dependent on what you want to catch. The first part of the season will be primarily for kings whereas by november it is primarily a steelhead game. October is generally a zoo and a time i avoid. November used to be less crowded but it is still relatively crowded in a lot of spots. DSR may be less so during that time as the bulk of fish are concentrated upriver. Can also be a good time to fish the middle river.
If you want to fish for salmon i would try to go in the next few weeks before it becomes a total madhouse. They usually release water labor day weekend which can bring fish in. Personally i would prefer to fish to fewer fish without crowds but your tolerance may very. The early fish are more inclined to bite.
As far as gear i primarily swing with two handed rods. It isn't an overly deep river so scandi heads with poly leaders work fine in most spots.