This is basically my approach in a nutshell +iCloud:
Image
TOP works with Dropbox, Box, Google Drive, OneDrive. I mainly use it to move stuff between each service. Works well enough.
Ok seems nice and works for you, however I want all my stuff in one place as it is already backed up on an external drive, however I do not know what platform is best. I decided to start getting rid of movies I am so bored of watching, music I never listen to Willie Nelson (Ex-Wife's stuff) and cleaning up all my apps as I want to be able to live in the 512GB Max spectrum, but I am down to 998GB from 1.2 TB. So can get more streamlined between the external WiFi drive and clean up the clutter, I will be ok.