Blueprint Construction Script Runtime Costs

I just want to clarify a few things with regard to Blueprint construction scripts and if they have any runtime costs (as opposed to editor time/cook time):

Does spawning actors in a construction script have a cost? ie spawning fence meshes along a spline.
Does rotating actors or changing their visibility flag have a runtime cost?
Does creating dynamic material instances have a runtime cost?
If the object requires replication across a server and client does that change anything?

I’ve heard conflicting things: that construction scripts run post load and that they’re static after being cooked. So i just want to make 100% sure before i start creating content.
Obviously this is only talking about statically placed environment blueprints and not ones dynamically created.