The latest patch is Version 1.172. Online play requires using the latest version. The Steam version already has this patch.
Extract mods to the Modules folder, then select the mod from the drop down menu in the launcher.
To increase the limit of how many troops can be on screen at once, download. Battle Size Changer. It increases the limit to anywhere from 150 to 1000. It is best to stay below 300, as higher values may cause performance issues.
Floris Modpack is a comprehensive modpack containing lots of mods which improve the game in almost every way.