Larry,
You could use any scale position over certain chords in a key. There are 7 positions of the major scale (2 positions overlap). Of the 5 unique positions, each one corresponds to a CAGED major chord shape. All the other chords in the key could be found with another CAGED shape in that vicinity. So the only general rule would be to use a scale position and chords in the same vicinity at various times in your song. You could go to another CAGED position and, again, find all your chords in another area of the fretboard at another point of the song. To build dynamic excitement in a solo you may want to move to higher positions during a solo and return to a lower position to resolve. Learning CAGED chord shapes, triads and arpeggios are the key. This all involves some theory and work, so, sorry not simple. On the bright side, you can create a lot of good music in one or two positions, so, like Brian says, “don’t try to drink from the firehose”. Hope that helps answer your question.
John

In fact, any “extended” position of six contiguous frets anywhere on the fingerboard always “contains” all twelve scales! IN other words, you can play all twelve scales at that extended position.
I have always considered that to be one of the most mind blowing things concerning the guitar…

Try it, it is very difficult but very useful!