There are so many pages, so it may be probably mentioned here, but anyway:
Will Bohemia start Utraquist? After granted authonomy by Emperor Sigismund and the pope (later the popes took their approval back, but no one cared anymore anyway), majority of Bohemian population become utraquist, which later coexisted and merged with protestantism. Almost 100% Bohemian and Silesian population were protestants, with Moravia having slightly less number, so please, don't even try to apply any form of catholicism or catholic system mentioned in the first post on Bohemian lands. (for example, last archbishop left Prague in 1419 or maybe 1420, as Jan Rokycana - the hussite archbishop - was never confirmed in his office by the pope) Thanx.
(tip for reading: Hugh LeCaine Agnew - History of the Czechs in Bohemia).
I see lot of was wrote about the secularism, yet I think it is quite difficult to decide whether to put it in the game as a religion, or not.. Secularism in medieval times was a form of a vacuum, just look how islam spread in bogomilist Bosnia, or how protestantism overcame utraquism in Bohemia itself.