As noted previously, there was no Nicean king in Western Europe until Clovis in 496, save for those in Ireland. Thus no orthodox royalty. But there were great leaders of the Western European Church. Saint (s) Martin of Tours ( the reliquary of his skull is pictured above), Saint Gregory the Great, Ambrose of Milian, Augustine of Hippo, and Isadore of Seville.
Gregory was a Roman Senator's son. and had a monastery built on his property. He was the administrator of Rome ( Prefect) at age 30. He wrote the authoritative biography of Saint Benedict of Nursa, and is known for his orthodox hymns and sermons. As noted before, he sent Augustine of Canterbury to convert the Anglo-Saxons. The strength and beauty of Saint Gregory's hymns and sermons cannot be overestimated.
The above video is very informative as well as illustrating his faithfulness to the dogmas of Christianity. The video below is Lauds from Holy Saturday, prayed by the Liturgical Institute at Mundelien Seminary outside of Chicago. It is how Gregory the Great prayed publicly. The hymn used is composed by the great saint, and the hymn illustrates how liturgical music show always point to orthodox doctrine.
The above prayers are part of the "Divine Office." The Liturgy of the Eucharist is certainly the summit and source of Church Life, both in the East and West, but it is the Divine Office that keeps Christians centered throughout the days, weeks, and/or years of his/her life. The Divine Office is composed of two psalms, a canticle, a Gospel passage, intercessions, the Our Father, and a closing prayer. The prayers were organized by Benedictine monks as well as diocesan clerics from Rome. The order of the psalms are now fifteen hundred years old, and are indeed heavenly. They are ordered to the feeling of each Liturgical Season ( the above prayers, for example are very somber because they are prayed on Holy Saturday morning, when Christ was yet Raised. Other psalms, like 118, are very joyous, and sung during the Easter Season).
Photo Credit: https://anastpaul.com/2019/09/10/saint-of-the-day-10-september-saint-ambrose-edward-barlow-osb-1585-1641-martyr/