From what I understand, Makaton is basically a sign language designed to be as iconic as possible, for people who have trouble understanding or using non-iconic symbols.
Whether it would be the best option for you would depend on what exactly is interfering with using speech effectively. If it's mostly an issue with generating fast complex movements, you would probably be better off using a typing-based system, because sign language movements are pretty complicated too. Plus, if you can type without issues, anyone capable of reading English can understand you.
If it's that you'd find a visuospatial system easier than a verbal one, then any sign language would work. In which case I'd recommend whichever sign language is most likely to be understand by people you interact with. Whether that be Makaton, or ASL, or any other sign language.
If you find your ability to connect symbols to meaning starts breaking down when you're overloaded, Makaton or maybe even a picture-based system (such as PECS) might work best for you.