I can basically just confirm what @theunis says…
When I left SA about 3 years ago I did research and at that time Capitec was the cheapest. Their actual transaction fee was around R40 for ATM withdrawals (though I see theunis says it is now R45), but the key was that they did not charge any currency conversion fees.
Some of the other banks had a little lower transaction fee, but all of them charged a 5% currency conversion fee on top which made the transaction very expensive.
For the past year I have been using a local bank in Thailand as I have sort-of settled down here for a while, but before that I used the Capitec bank card all the time and never had a any problems. I had to use it again about 3 months ago and all still worked fine.
Just make sure you tell them that you will be using it overseas for an extended period, so they don’t block the transactions as suspicious.
I would suggest though that you have a backup card from another bank just in case…
Edit: BTW, if you are going to be in Europe exclusively you can perhaps look into FNB’s Global Account which is a foreign currency based account (https://www.fnb.co.za/travel-products/global-acc.html). That should protect you a but against the Rand fluctuating, and also since it is already in the foreign currency there should be no currency conversion fees. Not 100% sure about the details though, so just enquire at your bank.