Since it's the top of the coil that is the receiving antenna for *anything* (re: Bill Lawrence) - the string excursions (vibrations) as well as any floating RF (electronic devices, lights, etc) - a narrow coil will be more focused on the true signal and less on the humbuzz. This is why big, wide, short single coils (P90, Jazzmaster, etc) always seem to be excessively noisy and tall, thin coils (Strat, Tele, etc) seem to be less noise prone.
The character (tone, output) of a pickup is based on more than a few factors. For the most part, Fender pickups dictate the footprint that is standardized and can't be changed or the resulting pickup most likely won't fit well in a guitar body rout or pickguard or bobbin covers. Next would be the bobbin itself and doing it Leo's way of a vulcanized fiberboard build held together by rod magnets will not be the same as a plastic bobbin with rod magnets stuck into the plastic, where the difference is how close the coil wire will be to those rod magnets and what will be the resulting shape of the coil wire. While the footprint of the bobbin won't change, it's height can be, and the results could be a taller, thinner coil of wire that's less prone to the humbuzz. Magnets in passive pickups have only one job - magnetize the strings. There's a sonic reason why Leo went with the weaker AlNiCx family of magnets and not ceramics. Not all coil wire is the same in that although the AWG wire spex require that the copper is to a specific diameter standard, the insulation surrounding that wire can vary greatly in thickness, and this coating difference might make a difference in the pickup's overall "character", perhaps when combined with other factors.
Besides all of the aforementioned, the main regulator of tone and output is the choice of coil wire gauge and insulation, the amount of coil wire around the bobbin, and the coil wire winding tension.
The character (tone, output) of a pickup is based on more than a few factors. For the most part, Fender pickups dictate the footprint that is standardized and can't be changed or the resulting pickup most likely won't fit well in a guitar body rout or pickguard or bobbin covers. Next would be the bobbin itself and doing it Leo's way of a vulcanized fiberboard build held together by rod magnets will not be the same as a plastic bobbin with rod magnets stuck into the plastic, where the difference is how close the coil wire will be to those rod magnets and what will be the resulting shape of the coil wire. While the footprint of the bobbin won't change, it's height can be, and the results could be a taller, thinner coil of wire that's less prone to the humbuzz. Magnets in passive pickups have only one job - magnetize the strings. There's a sonic reason why Leo went with the weaker AlNiCx family of magnets and not ceramics. Not all coil wire is the same in that although the AWG wire spex require that the copper is to a specific diameter standard, the insulation surrounding that wire can vary greatly in thickness, and this coating difference might make a difference in the pickup's overall "character", perhaps when combined with other factors.
Besides all of the aforementioned, the main regulator of tone and output is the choice of coil wire gauge and insulation, the amount of coil wire around the bobbin, and the coil wire winding tension.