Less dense, and consequently lower weight, yes, longer no.  Larger in diameter, yes, due to better fill out of the cavity, and a bullet might be a very tiny bit longer due to the same, but there's only X amount of space in the mold, said space just gets filled a wee bit better.  Volume is of the mold cavity, stays the same.  Mine are running about 10gr lighter than what the same bullet would weigh in WW.  There's a bit less shrinkage as the alloy cools and solidifies vs an alloy with more lead.