How are 'Not Mineable ' cryptos able to verify transactions? NEM, Stratis, BitShares are 'non mineable' cryptocurrencies.

How do they verify transactions if there are no miners? Maybe nodes only? Or... what am I missing here?

I ask because I assume with a non mineable currency I believe miner fees, aka transaction fees, would be super low. Transactions would also clear faster. Like Ripple. Takes about 10 seconds to transfer XRP.
I'm not sure about Ripple, but I know IOTA specifically uses each transaction to confirm the transactions around it. So instead of a dedicated miner, each user is essentially a "miner" for the short time they are making a transaction.