IMovie is about the easiest to use, there's no requirement to shoot your videos with an iPhone or Pad. I do run into things I can't do easily in it, especially related to integrating separate audio and video feeds. I use it with video I shoot on my Nikon. DaVinci Resolve also seems reasonably straightforward. For more heavy lifting I use Premiere Pro, which is not free, but comes with the other Adobe software I need. It has a significant learning curve, which I have not climbed. I'd guess the Apple's Final Cut Pro is also very capable and probably easier to use.