We often have customers who want to switch from classical guitar to steelstring guitar. Soon the question of the neck width comes up. Of course the player of a classical guitar would not give up the comfortable playability when switching to the acoustic guitar.
However, to set the neck width of a steelstring guitar the same as for a classical guitar would be a fatal error, because steel strings are much thinner than nylon strings.
Suppose a classical guitarist is good with a nut width of 52 mm, I would recommend a neck width of 48 mm for the steelstring guitar. Then, the string spacing is mostly similar.
A guitarist whose classic guitar has a neck width of 50 mm nut width, I would recommend 47 mm for the steelstring . 46 mm works as well, however, sometimes been perceived as too narrow. However, this also depends on the neck profile.
Nut widths over 48 mm are not recommended for steelstring guitars because the string tension of steelstring guitars is much higher than nylon strings. This makes it very difficult to play Barre chords on extremely wide necks.