I suggest reading this little gem:
https://www.campusfive.com/swingguit...ng-guitar.html
If you're to play unamplified in the style of the 20s-40s, I'd say your pick is between Monel and Bronze, both roundwound. My own Loar LH-700 is strung with Martin retro 12s because it is equipped with a DeArmond FHC and bronze strings do not balance well with that pickup. On my other archtops I have GHS vintage bronze 12s. They sound very nice acoustically and they also sound very well and well-balanced through my Rhythm Chief pickups.