The 70-200/4 is a fine lens, sharp and well made, but not a lot of reach and no Image Stabilization.
OP, I'd look hard at the 70 or 75-300 Canon with Image Stabilization, if that fits your budget. It will be more useful for what you describe wanting to shoot. Forget about using any teleconverter with it, though.
Actually, you can use any f4 or faster lens on any current Canon camera with any 1.4 or 1.5X teleconverter, including Canon's own, and still have auto focus work (center AF point only).
A 2X Canon TC, and possibly some others, will turn off AF with any lens f4 or slower. But, AF is slowed down considerably anyway, if you can even get it to work... maybe in ideal conditions.
The reason is that a 1.4X loses one stop of light. So an f2.8 lens becomes an effective f4 lens, an f4 lens becomes an effective f5.6, while an f5.6 becomes an effective f8.
A 2X loses two stops of light. So an f2.8 becomes an effective f5.6 and an f4 become an
effective f8.
With just a few exceptions, Canon cameras need f5.6 to auto focus, and are limited to the center focus point only at that slow speed. You can fool the camera by taping off some of the contacts on the teleconverter, but that doesn't change that the lower light makes AF slow down, less accurate and more inclined to hunt.
The exceptions are 1-series cameras and the EOS3, all of which can AF with lenses as slow as f8, I believe also center AF point only.
Zooms are less likely to work satisfactorily with teleconverters. Prime lenses work better with them, because their optics are less complex.
I use 70-200/2.8 IS with Canon 1.4X II teleconverter and think it works well (but not as well as a 300mm prime lens all by itself).
I also have the Canon 2X II, but won't use it with that zoom. there's just too much loss of image quality for my tastes, with this combo. I do use the 2X with 300mm and 500mm primes, where it performs very well.
Oh, and forget using a teleconverter on a 200mm lens on a 1.6X crop body unless you also plan to use a tripod, or unless the 200mm lens has Image Stabilization.
OP, you started off asking about "Macro". Please understand that a lot of zooms get a "macro" label that's a pretty liberal use of the term. They hardly ever get to magnifications that are truly macro territory. So, it's more a marketing gimmick than a truly useful feature. Best thing to do it look at the lens' specifications. Check the closest focusing distance. Compare with other lenses you are considering. Lens that focuses closest among others of the same focal length, will give you the highest magnification.
Besides, you can add extension tubes to just about any lens to make it focus much more closely and give you higher magnification macro or near macro shots. The longer the lens' focal length, the more extension tubes you need. I recommend the Kenko Macro Tube Set DG. It's a good value at about $160. I think Adorama might have a Pro-Optic set that's similar.
The $30 to $60 no-name tube sets on eBay are not good. They don't have the electronic contacts for auto focus or aperture control, which makes them pretty hard to work with.
Don't confuse macro extension tubes with teleconverters. They are not the same thing (Canon confuses things a little by calling their teleconverters "Extenders"). Macro extension tubes have no optics inside them. They just move the lens farther away from the camera body and that makes any lens focus closer and render higher magnifications.
and don't mind practicing a lot...
