I have been using IWP for a while now and i have to say it is the best option for managing multiple websites at once.
I used the manual self hosted option and the setup was effortless, which I can’t say of many webapps out there.
Other options out there like MainWP and ManageWP limit the set of features you get access to and/or the interface is not well tested. You have to click five times on update and half fail.
You can find IWP at : https://infinitewp.com