Althea puts me to mind of a heavyset, middle-aged woman, which sounds awful but isn't really, I guess because I think of a very bubbly, friendly, heavyset, middle-aged woman.
Althea Joy is definitely the best of your combos. I don't see
Joy as being fillerish at all; that honor is reserved for
Rose,
Grace, and
Elizabeth. I'm not wild about
Althea Kate, maybe just because
Kate is so overused as a fn these days.
Althea Lily is rather awkward. Therre are too many Ls, I suppose.