True they nailed it with the iPad I love mine. I use it more than the iMac now
Sorry to hear you have had issues transitioning. I have been using Macs since 1996 and continue to use Windows PC at work so have evolved with both OSs. But it qualifies me, I believe, to pass considered judgment on both OSs. And without doubt the Mac OS is the less clattered, faster and more intuitive of the two. Added to that the overall general lack of malware on Mac OS (because partly due to the way the OS sandbags third party software), and most of my Macs still run as fast as the day I bought them.
Give it time. You will get the hanf of it. One very simple tip would be to use spotlight more if you don't like Finder. It takes a bit more discipline to name your files in a more logical way but it should help. With regards to music and pictures, the 'abyss' is purposefully built in to stop Jo Public messing things up. But you can do things to allow you to see these files in Finder.
Dare, I say though given your leaning toward the iPad for everyday use, your computing needs are not particularly heavy duty anyway so perhaps you are not really getting the best out of such a beast of a machine?