“holy water”
Since the Bible has ZERO reference to Christians using “holy water” for anything, that seems to fall into the “catholic made up stuff” category. But, water certainly does play its part in baptism of believers.
As for the ability of “blessed water” to allow a believer to “bless themselves with it” or “absolve us of our venial sins and protect us from the devil”, well, ONLY the Blood of Jesus on the Cross takes away sin of ANY kind and redeemed believers are already protected from the devil by the Spirit of God that dwells within them.