each faction has a unique stratagem, i myself still charge like a hero lance at hand towards the enemy at it work's perfectly as polish.
Way it work's is cossack's are ranged cavarly, khanate are good marksmen and so are the russian's, though the russian's seem to be the F&S equivilant to swadia in the respect they are heavier armoured and seem to be generally more powerful unit's. while as pole's are great cav (just remember to not go dead straight at them, you'll lose 2-3 men on the charge, but if you go at a slight angle you'll be fine, remember DON'T bring a sword, 3 grenade's and a lance work's perfect as when horse dies which it normally will, you'll instantly replace the lance wiv a saber from your saddle giving you a average melee weapon, this only seems work wiv certain setup's of weapon's though) while as swede's are like rhodock in ideal they are well rounded and therefore benefit from a balanced army.
My strategies for the 2 i have used in depth (poles are my fav just because they're story is about being a bad ass war hero instead of a secret agent man like russia's) is that with the pole's a full contigent of cav work's perfectly, equip wiv lance's and pistol's and you'll be fine as they need fast pace shooters and something able shoot on move while on foot. in battle's your the equivilant to twice your size but in siege it's a bit pant's so be careful wiv that as NPC's don't receive the same "saddle Saber" benefit you do. With the russians i find best just to keep a firing line in a high ground which would slow npc cavalry's advance, their by far the best ranged unit's it seems, as they are also very capable melee fighters (do take in mind my character lives off the interest of my trade making's of nearly 2mil so i'm richer than the country i serve) as with the best armour and a saber and shield an attack reaching you ain't a problem and usually if it's a battle you have even a 1 or 2 advantage you may rout them before even getting to you, while as in siege they are amazing! but it does mean doing the obviously int biased story for the muscovites

also another thing, if you follow this the wooden fort thing work's great wiv the russian's but wiv the pole's it just fail's so as the pole's stay on the offensive at all times!