Lambda the Ultimate

IIUC in ML lexical binding of variables leads to a copy of the variable, whereas in Scheme it is a binding to the variable memory location itself. Is there a common terminology to differentiate between the two different kinds of bindings? Am I understanding the difference correctly?

It also seems to me that the ML approach has a positive effect from a software engineering approach because it doesn't lead to a strong implicit coupling between modules. Has that idea been explored in the literature?

I am thinking of using ML style closures in my next language, what is the modern thinking on such an approach?