I try to arrange the tabs I offer on this website as standard as possible. If you have the knowledge to read classical notation than there is enough information in the notation in the upper staff. But because tabs seem easier to read, not many guitarists read the classical notation. But my advise is to, at least, learn to read the rhythmical notation in the upper staff and to be aware of the fact that the notes with the stems going down reflect the bass notes and should be played with the thumb. Notes with the stems pointing upwards are the melody notes and should be played with the index finger and the middle finger.
Chord boxes
Most of the time chords are played with standard fingering. G chords are mostly played, by most guitarist, with the fingering as shown in the second example of the G chord.
But most of the times in fingerstyle arrangements it's better to play the chord with the fingering showed in the first example (with the pinky!). The advantage is that you have the index finger free to play notes on the E and B (or G) string, while holding the low G and B notes (on the 5th & 6th sting because they should ring longer than only one melody note!!).
I always write the most logical fingering in the chord boxes and they should be read with a lot of attention which, in the end, will make it easier to play the arrangement, and keep other (bass) notes ring as long as they need to ring.
But most of the time its enough to use only one finger to play the G chord en you might read G(3) or G(4) as written below, because most of the time you only use 3 strings to play a chord and I try to make that clear in the chord boxes, so you'll see 'strange' chord notations most of the times because I only show the strings (and notes) in the chord boxes you really play/pick/strum and the fingers you should use in that special case.
Kind regards,
Robert Molema