A piezo pickup senses vibration through the saddle, so string material doesn't affect whether it works. Choose strings the same way you would for an unplugged acoustic: by gauge, feel and tone.
A magnetic soundhole pickup works like an electric guitar pickup and responds to the magnetic parts of the string. On bronze strings, that's mainly the steel core and the plain steel top strings. Some soundhole pickups are voiced for bronze strings, so balance varies from one pickup to another.
Practical tips:
- Unbalanced string volumes through a piezo: check that the saddle sits flat and the strings are seated. That's a setup issue, not the strings.
- Uneven output with a magnetic pickup: adjust pickup pole height if it has them, or ask the pickup maker which strings it's voiced for.
- Too bright plugged in: try phosphor bronze instead of 80/20.
S.I.T. options: P1254 Light in Phosphor Bronze or GB1252 Light in Golden Bronze 80/20.