Not sure about FB or Twitter, but I personally use Followliker for managing IG accounts. It's simple to use, and it has extensive features that will allow you to manage your accounts effectively. As a note, I always set a longer/slower interval in posting, in order to avoid the account getting flagged for unnatural activities in the process.
There are a lot of tools out there, at the end of the day it all boils down to your needs.
You can use to ContentStudio schedule and publish content to Facebook, Twitter, Linkedin, Tumblr, WordPress etc.