I used the Travelex card during the pilot phase, and largely it was ok but there were a few occasions when it didn’t work at all, or declined but then worked on second or third attempt. I guess it may be down to timeouts on authorisation- especially if going across two systems. So the prepay option is probably more reliable.
Unfortunately Supercard have lost their unique selling point with the ATM charges, I hope Mondo keep their card free for FX use but this looks unlikely with the comments pinned on the Travelling with Mondo board and not answering questions about their long term plans.
I did order another Supercard though and will see how that goes - there’s also Revolut which is free for low volumes of cash withdrawals- I know some users have reported problems with that one, though personally it has worked for me.