All very useful input - thanks.
Any recommended books for an iMac beginner? The man in the Apple shop thought OSX/Mac for Dummies likely be too simple given the questions I was asking! Retired electronics engineer now, always had a gentle interest in PCs etc, wrote some Visual Basic stuff in the past but not into that sort of thing now. Just general PC work, email, surfing. Might buy myself a Raspberry Pi to play with.
I will retire into the background whilst I give all of this some further consideration. I hope no-one will mind me resurrecting this thread, or starting a new one, in the future when I inevitably go into all this in more detail.