This mod is finished and is not planned to be developed anymore.
2,3 - these are some developers decision to bring balance and a historical accuracy ( i think its most perceived factor in this mod - unlike wfas which focuses on fast balanced esports like playstyle, Deluge is more clunky, slower, darker and yet more demanding in certain actions to do eg. Shooting cannons, carrying large weapons, reloading muskets, building fortifications etc.
Factions tends to present historical accurate vibes with weapons and armors, unit formations etc. They try to mimic the real feeling of warfare in middle XVII century. Eg. You asked about Muscovite Tsardom: firearms wielders developed from early XVII century, so they are more orginazed in imitation of west countries: equiped with greater firearms, unificated clothes such as piechota nowego stroja, reiters. They lack of great and swift horses as PL Commonwralth though.
You should really try out this module and play some events every tuesday - its fun!