Hey,
poly count is ok for EU4, it should be slightly lower for CK2 to be on par with the vanilla units.
Attachments doesn't work the same in CK2 as it does in EU4, meaning that it is really difficult or even impossible to have them in a mod. In EU4 you can script them to a locator or a bone in the mesh by writing the following in the entity you want it attached to (the parent):
Code:
attach = { joint1 = "sword_entity" }
For CK2 the easiest way is to just include the weapons/attachments in the skinned model and export them as one mesh, regardless if the model needs to be using different weapons.