I enjoy playing Lithuania in MEIOU (with a bunch of submods) and giving the middle finger to all religion and staying with my pagan ways. While at the same time, playing semi-tall (which is vastly better in MEIOU than vanilla) and becoming a civilized pagan nation. The last pagans of europe, all while holding back the spacemarines that are nearby. One game had a bunch of sunni rebels invade to try to convert me, even though they werent even my rebels but white horde turned orthodox somehow, and so I beat the rebels back and declared war on white horde who became sunni again and forced them to be pagans too, they refused so I took them over and converted their provinces. They shouldn't have sent rebels at me, so I had to get them back for that.
Its my favorite nation in MEIOU, despite pretty much 0 flavor for them. Though I did change their stupid decentralized vassals to normal vassals. Decentralized vassals are a stupid BS mechanic that ruins any nation that has them. I found every decentralized vassal in the diplomacy history and changed them to normal vassals. Luckily not that many exist. Its the worst mechanic in EU4/MEIOU. Almost no one likes lithuania because of their stupid default vassal setup, so have to go in and fix it along with the few other nations that have. I guess its cheating, but whatever I give a big middle finger to that stupid mechanic. You can tell I really hate that mechanic lol.
rant aside from that dumb mechanic that really triggers me...
This is in regards to MEIOU, vanilla isn't very good for tall in comparison. Lithuania is a ton of fun really if you play it mostly tall. Its pretty easy to build up a strong capital (and have the best city in the world), with good provinces around it. I also like to keep Trakai has a march, since they share the same traditions and are closest allies to Lithuania and they make a powerful march to help defend that border. Besides that, sometimes Crimea pops up (quite often usually) and you can cut through them to get the black sea. That is the easiest target to get sea access because otherwise you start landlocked and the spacemarines are too scary to war against early on. Crimea sometimes never shows up though.
But honestly, out of all the "pagans", meaning not christian/muslim or any other major religion...lithuania is probably best to shun the religious world and stay as pagan. But it does have its challenges, much easier though than other non major religion nations. Like aztecs/incas start good, but the smallpox plagues kill them, which makes them have an easy beginning, godlike challenge mid-game and only recovers toward late game. Where as lithuania is okay early, and slowly gets better as they build up good cities. The hardest part is dealing with the spacemarines