Is Streamfab easy to use? Yes, and no.
From a basic end user perspective, you should be fine. Just remember there are two settings areas that need to be changed.
General:
For Youtube stuff, and sites like that
VIP Services:
For the VIP Services (Amazon, etc).
Go through all the settings in those two categories, and understand that videos are saved in different locations based on what you're saving (it is confusing)
The rest is pretty much just like your browser. Login to site, select video, Streamfab looks to see what needs to be / can be downloaded and you're on your way
If you're an advanced user, or if you use OneDrive (many people do), you'll find the settings frustrating, as there is a constant battle waging between Streamfab and OneDrive over Documents. Even if you change the basic stuff (it can be done), StreamFab still caches files where it shouldn't, among other things. Brought this up , repeatedly, only to have it dismissed by support, so, from a technical perspective, I'd say no, it's not easy to use, and support doesn't care
That said, scroll through the streamfab forums. You'll see problems, and resolutions, so, in many cases, it CAN be used. I've done so for over a year now.