Hi @AM13 ,
Nick here from Shopify.
Really good questions! I completely see where you are coming from if your client base is mainly in the US and Europe. If it was me I would stick to keeping things with your native currency as that is where your business is set up and registered. I would recommend using one of the gateways Shopify is partnered with, in South Africa which you can see here.
You can change your currency if you like, but what you get paid out and what kind of bank account you need to accept it depends on the payment method you are using to collect the money. You can set your store so your customers see their native currency with a currency converter app from the Shopify App Store. The checkout would display in ZAR though.
Hopefully, this helps answer your question and gives you an idea of the next steps to take.
All the best, Nick