Do we have info on how the level of the rebel towns walls? And how many guys it has.
We do not know.
You asked about walls, so I'm going to tell you about sieges in R:TW.
A town can have one of five levels of walls: wooden palisade, wooden wall, stone wall, large stone wall, epic stone wall.
A town must be at the town level for palisade, large town level for wooden wall, minor city level for stone wall, large city level for large stone wall, and huge city level for epic stone wall.
With any army, you can lay siege to an opposing town. The town has food stocks to last for a certain number of turns, based on its wall level. If the siege is maintained for a that many turns, the army inside the town dies and the town is taken. The sieging army can be driven off and the siege broken if it is attacked and beaten (be it by forces from inside the town or outside). Similarly the siege can be ended early if the attackers manage to kill the defenders. This can happen during one of the defender's attacks or when the attackers assult. When laying siege to a town, your army gets a certian number of build points, the more people in the attacking army the more points. These points can be used to build siege machines. They are as follows:
Ram (50bp)
Ladders (15bp)
Siege tower (75bp)
Sap point (75bp)
Against both types of wooden wall, the only machine available is the ram. The walls are not thick enough to stand on, so ladders and towers are useless. Similarly, they do not have proper foundations, so sapping (tunneling underneath to destroy the walls from below) is useless.
With the stone wall types, all four machines can be built. Stone walls are thick enough to stand on, so combat takes place on the walls. An attacking army on the walls can then capture the gatehouse and towers along the wall. Towers fire automatically and without any troops stationed in them. Stone walls and higher can pour boiling oil from the gatehouse on opposing troops that assult the gate, so rams are not advisable against stone walls or higher.
Siege machinery like onagers can be built later on, but they are an advanced unit type.
Any questions on sieges?