Completely depends on the Muslim.
I know LOTS of Christians(?) who smoke, drink, curse God, commit sexual sin and claim to be a christian simply because they live in a christian culture.
Is there a separation of sacred and secular in their lives?
Islam AS A SYSTEM does not differentiate between the secular and the sacred. In the Middle Ages, Europe had ecclesiastical courts -- legal institutions in which violations of sacred mandates were judged. These were separate from civil courts, where the more common charges were heard.
That has never been the case in America. "Congress shall make no law ..." and all that. And even in the most religious of European countries these days, religious courts have little or no power, where they exist at all as anything but relics.
That has never changed in Islam. The Taliban and the theocracies of Iran, Saudi Arabia, Iraq, and Pakistan are living examples. Violations of religious mandates in those countries ARE violations of law. There is no difference.
Christianity makes it clear that Christians are to "render under Caesar that which is Caesar's, and unto the Lord that which is the Lord's." It not only permits separation of church and state, it commands it.