Were these fortifications expected to be battle sites, or were they more like the Great Wall of China in that they were less warzones and more barriers to restrict the movement of an opponent who primarily consisted of mounted raiders/soldiers?
Not much. Russian firepower is one thing, there might be many layers of walls, fences, obstacles and ditches to slow them down. They may also use mud to cover up the wood to fireproof it.
In more elaborate defenses (though not in the defense you’re asking), bronze or copper were used to armor the wooden parts