Regarding the ukulele range this post might be helpful:
http://just.4str.in/ukulele-tuning-pitches/
Yet the charango question remains open....
According to
Wikipedia the charango stringes are usually tuned G4/G4, C5/C5, E5/E4, A4/A4, E5/E5. The highest possible note depends on the number of frets, e.g. on a 16 fret charango you'd have G6 (16 half tones above highest string).
Standard ukulele tuning is G4 (G3 for low-g), C4, E4, A4 - slightly below the charango.
All other things being equal, construction + scale length + tuning + strings = tonal range...............maybe!
Construction can be left out, tonal range can be determined mathematically - the only relevant factors are
- lowest open note (e.g. C4 on a standard, re-entrant tuned ukulele)
- highest open note (e.g. A4 on a standard ukulele)
- scale length (number of frets, not physical length)
Tonal range is from lowest open note up to highest open + scale length (1 half step per fret)