Erm ....
Let's start again.
Min Pentatonic - Starts on the root (say A, for Am).
If you want a Maj Pentatonic drop down 3 frets and use the same shape - but don't forget that A is still the root (not F#)
With me so far ?
As for applications - use Maj Pentatonic for major tonalities, occasional blues that are written in major keys, ballads etc.
Blues playing is tricky to explain - but it just works - because usually we all play a Min Pentatonic against a Dom7 chord. Thee min scale shares a b7, and the min3rd is a tolerable note against a Dom7 chord even though a Dom scale has a Maj3rd - but our ears just accept it.
Ok so far ?
So substituions of other Maj/Min pentatonics is as much a matter of taste as theory - try what works for you - but if you want to understand it, or get some hints you'll need to do a bit of Harmonic theory, and look into TriTone subsitution.
Also, Dom7 Pentatonic uses the same trick as Maj Pentatonic, only up 2 frets rather than down.
I learned all of this from Clarky one freezing afternoon in his "studio" (the back bit of his garage !!!

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