Poland looks like a phenomenal religious/military victory civ.
The one military policy acts as wildcard policy allows you to found an early pantheon (without sacrificing the crucial +1 hammer), which gives you the boost to Mysticism, which allows you run the Great Prophet card (like Greece), and get your religion founded fast, on par with Russia's Lavra or China's Stonehenge.
Then you take Crusade or Defender of Faith. You forward settle an opponent and start building an encampment (maybe bring a worker to chop it). You either A) have an easier time taking the city or B) an easier time holding the city after conquering it and/or C) can spend your faith on converting other cities farther back/away, since all you have to do is finish an encampment to convert that city.
So the converted policy slot and religious-conversion upon culture bomb have great potential just by themselves - but wait, there are like 5 other bonuses. The standard faith adjacency bonus from districts supports getting enough faith to get missionaries out and will be very reliable and controllable.
The Winged Hussar and the Sukiennence are great too. They have their downsides and aren't OP, but I view them very positively.
The Winged Hussar is at Mercenaries on the Civics tree in the late medieval era. Heavy Cav unit with 55 strength and 3 gold maintenance, costing 250 production. It can't be prebuilt or upgraded into, but upgrades into a tank. So your opponents will definitely get to knights before you can even sniff Winged Hussars, and Knights cost 180 production for 7 less strength than the 250 production Winged Hussar. But the Winged Hussar will clearly beat all medieval units once it's out and is vastly preferable to the 240 production/4 gold maintenance Musketman which comes later, has 2 movement, and requires Niter.
Unfortunately the policy card to boost production of Winged Hussars is at the bottom of the tree, at Divine Right, which requires 2 Temples to boost, a high opportunity cost boost. So it looks like a great unit but will take some time to get it out on the field, and if your opponent puts as much production into Knights as you do WH, he/she can build 7 knights for the same production cost as 5 hussars, not even considering upgrades from heavy chariots. How many turns are needed to allow 5 Winged Hussars to beat 7+ knights in a vacuum? Probably more time than it takes for them to tech to Musketman. But - you put Winged Hussar's together with Crusade and forward-settled culture bombs, and maybe a GG from those encampments - and you've got some easy cities to conquer. Or - the Winged Hussar will be wonderfully resistant to Crossbowman - they serve as fantastic vehicles for hostile religious conversions with Apostles behind the front lines.
The downside of the Sukiennence is that most of the time you want to use trade routes to boost a very young city, giving it extra production/food, but the Sukiennence only works for trade routes originating from the city in which it's built. You could chop woods to get a Commerce Hub and Sukiennence up fast in a young city, but generally speaking it will be best used to get enough gold to pay maintenance on all the Hussars you are putting in the field. Even 3 internal trade routes from a city with this will pay for 6 WH's in conjunction the -1 gold unit maintenance cost policy card, and you use the centralized production from those trade routes to help pump out the Hussars.
Playing against Poland, against an equally skilled opponent - do not forward settle them. Do not allow them to forward settle you - get your units out there in forward defense. Consider that you might have a nice window for a Chariot-->Knight rush since it is unlikely Poland will be making and paying for many Knights or Crossbowman if they are gearing up for Hussars (that said, I will still favor Defender of Faith as Poland). Get your science rate up early so you can tech past the Medieval faster than they can get WH's in the field. Get your own religion and have religious units available if your city gets flipped to Crusade from a culture bomb. Any other tips for playing against Poland?