Upper vs Lower Reservoir

Where do you think is the best area to start when learning a new lake in the summer, upper (near incoming river/creek) or lower (near dam)? Is there a difference if your lake has mostly white vs black crappie?

Lately I've been trying my luck on structure/open water in the lower half of a lake that's 35 ft deep max. Haven't had a whole lot of luck. Decided to try the upper end this weekend and the fish activity overall is much better there. I read this article Where The Crappies Are - In-Fisherman about the Kentucky Lake tracking study. The lake I'm fishing has black crappie. So now I'm wondering if I should focus more on shallower water, cover strategies. The upper end still has some channels of 20 ft deep with 10-15 ft flats nearby.