I don't have very strong requests from a photo manager other than allowing me to browse them, and maybe tag or annotate them from time to time. Hence Apple Photos meets my expectations. However, I understand that others may have more refined requirements and many apps are available on the market. Jack Baty probably tested them all. In a recent post, he suggested Mylio which looks like a nice way to manage digital content without any cloud backend. I may try it at some point.