Religions' map of Czechoslovakia, according to the 1930 census.
Religious adherence to the Catholic Church in Bohemia was very weak, even among self-professed Catholics. Even for devout Catholics and even in Moravia, Czech national culture was deeply tied to the Hussite heresy, and Jan Hus was revered as a father of the nation, regardless of his religious inclinations. As such, over the 1920s and 1930s, more and more Czechs would move away from the Church towards the newly-created Czechoslovak Church, various Neo-Hussite groups are identify as 'non-religious'.
Needless to say, relations between the Church and the Czechoslovak state were not easy in the beginning, given the anti-clerical or secular predilections of the main Czech parties (with the exception of the Czechoslovak People's Party) and their idolization of the Hussite movement. As a result, relations were very tense, although the state was not laïque or officially secular due to opposition from the CSL and the Slovak People's Party during the constitutional drafting period. In 1928, Benes and the papal Nunzio signed a 'modus vivendi', short of a concordat but a decent enough agreement to normalize relations.
The Czechoslovak Church is an interesting thing. It was founded in 1919 as a splinter of the Catholic Church. Originally a sort of modernist Catholic Church, advocating lay participation in rituals, the use of Czech in the liturgy and the Bible, the Church would also soon come to adopt elements drawn from Hussite tradition, other Protestant traditions and even Orthodoxy. The Czechoslovak Church was sort of the 'national' church in a way, as it was very closely linked to people like Masaryk or Benes, among other major politicians of the First Czechoslovak Republic. The Czechoslovak Church was, despite its name, a Czech and especially Bohemian phenomenon.
The Augsburg Confession churches (for there were 2, the Silesian one, mostly Polish, and the Slovakia and Subcarpathian Ruthenia) were Lutheran churches. The Reformed Church of Czechoslovakia was a Calvinist church, mostly ethnically Hungarian, and a splinter of the Hungarian Reformed Church.
About Jews, whereas Jews in Bohemia and Moravia as well as a good chunk of Slovakia belonged to the more secular, reformist strands, the Jews of eastern Slovakia and especially in the Subcarpathian Rus where Hassidic jews, and many times actively hostile to the work/presence of Zionists and secularized Jews. Many of them had crossed the Carpathian Mountains in the 17th and 18th centuries from Poland or Russia.
Rusyns were predominantly Greek Orthodox with a significant minority of 'Russian' Orthodox. Many Greek Catholic priests had enjoyed good relations with the pre-1920 Hungarian state, and as such as the Greek Catholic hierarchy was very suspected of being Magyarones (pro-Hungarian fifth column). For that reason, the Czechoslovak state encouraged people to become Orthodox. That went as far as having the Czechoslovak state organize the Eparchy of Mukacevo and Presov, attached to the Serbian Orthodox Church, due to historical ties and the fact that Russia and Ukraine were communist states. This was also supposed to help the Ukrainophile and Russophile elements of the Rusyn nationalist elites and help them reach the people of the region, at the time very backwards.