Is a "Smart" NIC worthwhile ?
Unless a computer has a heavy traffic load a smart NIC is not going to make much difference to CPU loading.
Some servers (especially shared ones in datacentres) have enough network traffic for the reduction in CPU loading from the use of a smart NIC to be worthwhile - however for most servers (and almost all end point devices (desktops,laptops,embedded computers etc)) the CPU loading caused by the network traffic is too low to make a smart NIC economic.