6. Is the JT7 easy to drive? Can it be powered by a regular smartphone?

Yes. The JT7 is designed with 18Ω impedance and 92dB/mW@1kHz (109dB/Vrms@1kHz) sensitivity, making it easy to drive by regular devices like computers and smartphones. However, working with professional-grade audio devices, like digital audio players, would bring better sound performance.