I'm late to this thread, but 100% Jadzia Dax. She's old and young, knows how to have a good time, doesn't take things too seriously, but has loads of guts and grit.
And also Kira Nerys. Tough, doesn't take any shit, isn't afraid to advocate for things she cares about. But also warm and hopeful.
I totally agree with you! Kira was tough, a resistance fighter but cared a lot about things too. Star trek really did have some great women characters!