I have never met Capuan as an adjective, except to describe someone from Capua, but it appears to me that there are two likely possible applications for the adjective Capuan (there could well be others!). One would refer to living in luxury (Hannibal’s men were seduced by the luxurious life they were able to lead in Capua). The other would refer to an all-or-nothing, do-or-die, never compromise, philosophy of life (the Capuan school for gladiators taught this approach). Perhaps the context helps…?