Pretty sure the mustang would have 19 frets. Fender J and P are usually 20. G&Ls come with 21. Ibanez SRs are 24.
I'm not aware of any 22 or 23 fret models. I think I might have had a Carvin with 23 frets once but I don't remember exactly.
For what it's worth adding more frets up there is basically to let you get in a guitar's range. Maybe you do some solos or rhythm chords. Some people use the expanded range of pitches available from having more frets.
So far I've preferred 21 the most. However, the advantage is small. Only for a couple songs I might use that last fret.
95% of the time I'm below the 17th fret. Above the 12th maybe only 20%. For little flourishes