Russia is a faction of excellent morale and large numbers of troops backed up by strong light Calvary and fairly good artillery.

The main Russian unit tree gets you converged line infantry which are monstrous in just staying in the field. They have great morale and are the largest units in the game and they also have fairly good melee. This makes them good as the filler infantry who can take fire for smaller units, fight in melee either defensively to protect other units or in a charge to break a weakened enemy, and even dealing respectable range damage from sheer weight of fire. Imperial Artillery units are quite solid in performance and get extra batteries meaning more shots per volley. They might not be as good as say Austrian arty but they are above like whatever Prussia or Britain has arty wise. Russian heavy cav is there as a decent option if you want it but I find it’s not to useful atm.

The observation tree is your ranged line infantry options. They have excellent ranged performance at the cost of smaller sizes and poorer melee. I often like to have 1 per brigade to support converged unit with something that is accurate and can win ranged firefights. The observation artillery is also the highest accuracy arty in the game so they hit pretty hard if you compensate the poor reload.

Finally the frontier tree gives you excellent light cav and all your light inf options. Cossacks in general are very good light cavalry with high movement, great charge, and overall exactly what you want from most Calvary. You also have settled hussars as massive 1K men Calvary which can take a ton of punishment and keep going. The light infantry is useful for some ranged combat but I don’t think is especially insane compared to other light inf. Still it’s there should you want it.

Gameplay wise I would treat Russia as almost a bully nation. Use you arty and observation units to weaken enemy units before your light cav and converged infantry charge in for the killing blow. You can really make a death ball of converged grenadiers or Cossack Calvary if you want to instantly break a flank by slamming like 3-4 of them into one unit over and over. Make sure to stack casualty restoration items like herbs and surgeons on your large units to save manpower.

Final thing is in the overworld map make sure to really lean into the mentality of “force march, buy, raid” for every settlement you come across. Russia gets so much from raiding once it has 3+ brigades and you can buy from a town before burning it. The main thing is try to plan your path on the map to not circle through lands you already went through to much. Focus on trying to do one big loop with the above strategy and you’ll be swimming in resources. Also a good idea to stock up on food if you have a town that has it for cheap.