Ah i see where the confusion may be.
public bool IsVisible
{
get => Function.Call<bool>(Hash.IS_ENTITY_VISIBLE, Handle);
set => Function.Call(Hash.SET_ENTITY_VISIBLE, Handle, value);
};
As you can see its a bool, but its also a property and is used the same way any other variable is used. Its not a method, as it does not have any parentheses after the variable name. So if you want to set the property it must be assigned to using = true/false.
As you can see you can also get a value from this property.
If(ped.IsVisible) DoSomething();
This can be similar to a method that returns a value of type bool.
public bool IsVisible(int handle)
{
return Function.Call<bool>(Hash.IS_ENTITY_VISIBLE, Handle);
};
A method can not be assigned to, but will return a value. So can be used in multiple different ways.
if(IsVisible(ped.Handle)) DoSomething();
For setting outfits the use of this native is required. https://alloc8or.re/gta5/nativedb/?n=0x262B14F48D29DE80