[Vulconizer]

This is going to sound wishy-washy, but :

Try both approaches. One after the other. See which fits your style the best and works for you.

Set out 1 mic at first. Record it. Listen back. Move until you hit your sweet spot. ( um, that didn't come out right at ALL. ) Try adding another mic if you feel it will work with what you want to hear. This is a time-consuming task, but it's worth it if it gets you the sound you want.

Listen through headphones and move the mic(s) around. I think this is a bit tougher as you're prolly gonna get a bit of the actual instrument leaking into the headphones alongside the mic sound, unless you have some headphones that provide great isolation. This may color your judgement of the sound that is actually coming through the mic(s). Record a bit and see what you come up with.

Have fun with it. Pretend you're a mad scientist and you are experimenting with getting the perfect sound in order to dominate the world with kick-ass music. An occasional evil laugh just makes it that much better...