Absolute magnitudes range from about 15 to about -5. That is a range of 20 magnitudes, that is 100×100×100×100, or 100, 000, 000, in energy output. The sun's absolute magnitude is about 5; the brightest stars are tens of thousands of times as bright, the dimmest tens of thousands of times dimmer.
Star sizes are generally not directly accessible. The size of a star's image in a photograph increases with exposure time, and so depends on the photography not the star. ("Stellar discs cannot be resolved.") Therefore size must be found indirectly. The primary tool is the blackbody property that the total radiation from a glowing object is proportional to its surface area times the fourth power of its temperature. This enables size comparisons to be made. For example, if two stars are in the same spectral class, the brighter must be the larger. If two stars have the same M (have equal energy output) , the hotter must be the smaller.
The largest stars are several hundred times the size (diameter) of the sun; the smallest are a few tenths as big as the sun.
Remember these are surface (photosphere) temperatures.
The hottest stars are 20, 000 degrees K and hotter, the coolest about 2 to 3000 degrees K. Some might be cooler,but they would be too dim to be seen.
The mass of a star, as with all other cosmic objects, is found by watching its gravitational effect on another object.
That is: find an object in orbit around it (a satellite), measure the period and orbital radius of the satellite, and use Kepler's third law. Only stars with gravitationally bound companions (double stars, or multiple stars) can have their masses determined in this way. The heaviest stars are 10 or 20 times as heavy as the sun, the lightest go down to a few tenths of the sun's mass. ( ``Heavy'' is not technically correct. The proper term is massive but heavy is commonly, if wrongly, used and understood.)