"While the authors of Ark initially imagined a very optimistic scenario where new rounds every few seconds, initial bootstrapping will probably have to happen with use-cases that can afford to wait multiple hours for an Ark transaction to confirm, if transaction fees are not subsidized."

I'm confused what these rounds are. How can they happen more frequently than blocks on the main chain? What are the practical implications of the rounds happening only once per day? Are vUTXOs always spent into a new round, limiting the number of transactions one can make?