1st thing is I always use my own mics. I use two. One on a short stand pointing towards the base of the harp. The second on a boom stand pointing towards the treble string, but not too close.
I have never found a way to get an even sound over the full range of the harp using a single mic. If I am trying to record I use a third from a distance to get the sound from the whole room as well.
I, myself, have a pickup permanently attached to the inside of my soundboard (which, frankly, I rarely use in wedding situations, because I just don’t feel it’s needed). But for many years before getting this pickup, I played for local community theatre groups and they often wanted to mike me.