You can very much be peaceful, and at peace, without a God.
The peace that God gives is not circumstantially based. It is peace in bad circumstances, in tribulation, in no health insurance, personal loss and in police breakdown — in societal breakdown -in the approach of death. It’s in and through these things believers have peace — the peace that passes all human comprehension.
Neither of which fundamentally necessitates a god, belief in God, or anything spiritual.
People can just be at ease the way way they can just be good people, without any religious or spiritual connotations whatsoever.
People may believe in a God, and it certainly helps some people who otherwise wouldn't be able to feel those ways in times of suffering, and that's great.