Practically none of it would be applicable (if using a commercial router). They all use hardware offloading, and traffic seldom touches the CPU. Only "logical" tasks are raised to the CPU, like ARP resolution and the likes (what’s called "trap to cpu").
If you’re doing custom routing with a NUC or a basic Linux box, however, this would gain massive power savings because that box pretty much only does networking.
Only if you're using busy polling. Very little software uses it, because it's only a good fit if you think pegging a CPU to reduce latency responding to packets is a good trade.
If you’re doing custom routing with a NUC or a basic Linux box, however, this would gain massive power savings because that box pretty much only does networking.