afaik different aircraft use different positions of fuel pump switcher and or mixture lever by default, and some of them use those positions as mandatory and other can be started with both positions mixture or and fuel pump… in msfs some models move mixture forward by itself when you start them
p.s. some time one aircraft can be started without fuel pump from one tank, but can not with another, just because from some tank fuel will not go to the engine(s) without pump, like p-38 wing’s tanks… so, different fuel system need different moves of pilot, for engine start/stay work