A TC changes the lenses effective magnification without changing the minimum focusing distance. You can't use a TC to turn a 70-200 into a macro lens.
Extension tubes shorten your minimum focusing distance, allowing you to be closer to your subject, which increases magnification.
My 100 macro is already a 1:1 macro lens, by adding the 1.4TC directly behind the lens and then adding 68mm of extension I'm able get close to 2:1 magnification.