Lad does refer to young men and boys but certain british dialects use lad for any male of any age also young women who behave like young men are sometimes LADETTES

Pretty much. The female equivalent is "lass." "Ah, spring was sent for lass and lad, 'Tis now the blood runs gold, And man and maid had best be glad Before the world is old."--A. E. Housman The poet uses "lass and lad" meaning "young woman and young man" in the first line, and then "man and maid" (man and young woman) in the third.

Yes, “lad” is used almost exclusively to refer to males.