I am replacing on older TV with a smart TV. Do I need the box with the smart TV?
Do you mean the set top box? Yes you do. The tv is not that smart yet 😀
It depends.
Newer TVs will have a qam tuner, so you can view local channels.
And if the smart TV has apps for the channels, you can use those with your fios login to access a number of channel content.
Outside of that, yes, you will need a STB to view FIOS.
