Learn English – difference between dose and fix

The word "drug" can have connotations of illicitness, whereas medication is always used in licit contexts. But a drug can refer to licit medicines as well. New drugs come on the market.

A drug is typically ingested (or injected) whereas medications can also be topical. Not that we don't say "topical drug" too, but "topical medication" is used more often and has been in use since the 1840s, whereas "topical drug" is a fairly recent usage, arising in the 1950s per Google ngram.

So, they're more or less interchangeable, except in illicit contexts, where drug is used. The criminal is said to be a "drug dealer", or a "drug runner", and the addict is said to be "hooked on drugs" or "on drugs". The patient is said to be "on medication".

The difference is in the degree of change applied to the object.

Enhancing leaves the main structure and functionality the same, most features intact, and generally speaking improves the object by applying small modifications.

Revamping often changes the basis, some fundamentals, some key features. Structure can undergo some changes, but the functionality generally is kept as is although we can see re-prioritizing of some elements.

Overhauling involves disassembling into constituent parts, examining each of them carefully for flaws, replacing with equivalent new parts (subsystems), in order to bring the system's performance closer to the original specification/idea.

Those words are not interchangeable. You could overhaul an engine of an aircraft to bring the engine back to its "factory new" performance. You could enhance an engine of an aircraft by replacing some heavier parts with lighter ones, for instance. You wouldn't revamp an engine. The latter most often used to describe a process for making fixes in a social/business system, like government, company management, etc. You could, however, revamp a design of an engine, which often includes technological part (manufacturing).