Yeah, I also don't think I'd really call Czechia a place with a "lot of Catholicism in its background." It was a hostile top-down imposition from the Austrians, with the consequence that Czechs are largely agnostic/areligious today.
Prior to re-Catholicization of the 17th century, there was a strong presence of homebrewn Hussite/Brethren Protestantism (mostly Czech-speaking people) and somewhat smaller presence of classical Lutheranism/Calvinism (mostly German-speaking people). There wasn't any clear geographic boundary between those two, the communities were mixed, though there were regional "strongholds" - e.g. Silesia was strongly German-Protestant while southern Moravia was strongly Czech-Catholic.
Orthodox communities, with the exception of ambassadors or foreign businesspeople, weren't a thing in Early Modern Kingdom of Bohemia.