Re: pickups & preamps
Popular pro options would include but not necessarily be limited to Scherltler Dyn M, McIntyre Feather, K&K twin. Some of these brands have suitable associated preamps, otherwise LR Baggs, Headway make decent DI/pres.
Remember that although you lose a mic stand, you gain cables and boxes around your feet.
Hereby & forthwith, any instrument with an odd number of strings shall be considered broken. With regard to mix levels, usually the best approach is treating the mandolin the same as a cowbell.