Ccleaner was working well before Andoroid 7 (Andorid 7 made some limitations), but now, I think that it is better to boot into Recovery mode and wipe cache partition (instead of any apps).
You can use Clean Master and CM Security applications to wipe out unnecessary space from your cellphone. These applications provides various other facilities like cleaning junk files, phone boost, battery saver and inbuilt antivirus.