I don't believe there is such a thing as "perfect pitch". Pitch is a matter of convention. Today we pitch, by convention, at A=440Hz The customary medieval pitch is A=415 Hz. So a person with perfect pitch and a time machine would enter today knowing the piano note just played to him was (say) A and come out knowing that the same note was nearly Bb.

You will get by with a capo and the following chords: -

A, Am
Bm
C
D, Dm
E, Em
F (maybe Fm)
F#m
G


Some are handy in more than one position. Occasionally Bb is useful.

7ths (technically, flattened 7ths) are not really needed in English folk song. In American folk song you can usefully add

A7
B7
C7
D7
E7, Em7
G6, G7

In English music I fairly often use D9 and A9. James Brown's rhythm guitarist made a living out of E9 and B9

The barre chords of course go all the way up and down.

And so to neck sets.

The problem is that first you need the neck relief (or progression) to be right. Put a capo on at the first fret, and using a finger push the string to the fret where the neck meets the body. Using feeler guages, measure the clearance beween the bottom E string and the fret at the 7th fret. It should be about 0.25mm. Adjust using the truss rod.

Or you could hope that it is OK - in which case the next bit gets a bit less precise.

Most guitar scale lengths are between 24 7/8 inches (typical Gibson) and 26 inches (some Japanese guitars) but more commonly 25 1/4 inches.

You need a straightedge 24 or 24 1/2 inches long.

Put the straight edge on the frets. Slide it towards the saddle.

At one extreme, it may just clear the bridgeplate, and slide to hit the saddle.    If it clears the bridge plate by more than a smidgeon it's bad - but that is most most unlikely, the laws of physics work in the opposite direction.

It is OK for the edge of the straightedge to finish up hitting the bridgeplate by about 1/16 inch, or even 1/8 inch.

If it is more - worry. Probably avoid the guitar.

If the straightedge hits the top (face) of the guitar before hitting the bridge plate - pass for sure. It needs the neck taking off and putting back on again different. This is not hard on most bolt-on necks (certainly most EKOs and some Hagstroms). It is a nightmare with a so-called "set-neck" where the neck is attached to the body with a "dovetail" joint.

Hasta la Vista.