We can obtain luminosity from a stars distance and apparent magnitude. We have some stellar images where we can resolve angular size, but mostly the Stephan-Boltzmann Law is used with a known temperature and luminosity to solve for area, and hence diameter. We must measure binary stars, and using Kepler's Laws of orbital motion, gravity interactions can give us stellar mass. Also, stars with the same spectra tend to have the sme mass. The thickness or width of the spectral line can indicate the amount of that material present in the star.
All stars rotate.
One edge is moving away from us, so is red-shifted, and one edge is moving toward us, so blue shifted. Spectral lines will appear broadened by this effect. The faster the rotation, the more the broadening. The Doppler Shift of lines in the star's spectra give us an indication of its motion toward or away from us. The star's spectra and inferred temperature and pressure clarify the stars atmospheric profile.