update: I edited question so that it will be mainly related to LTspice
OK, now I have used irfz44n for an example model, I realized that, by using the directive above(nmos), I am not able to modify Vto value. However if I use the second one(vdmos), I can control the Vto value. But while choosing the mosfet from component selector, I get it from "nmos" option. I wonder why this is the situation? Should I use
vdmos instead of
nmos all the time?