How does the wāw of wa-staghfirhu differ from the fāʾ of fa-sabbiḥ?

They are the same grammatical particle in every respect
Wāw alone is the conditional response and fāʾ negates
Fāʾ turns a verb into a noun and wāw makes it jussive
Fāʾ joins the response to the condition; wāw coordinates two commands within that response