Can a house account be settled on the POS, and does the customer know what they owe?

Yes to both. On the POS press Void or change, then House accounts, to record a payment in cash, by card or by bank transfer; cash goes into the open drawer as money in. The same is on the dashboard under Settings → House accounts. The customer gets a WhatsApp each time something is added or paid, your managers get an email, and what is still owed is in the day report and the monthly invoice summary until it is settled. A manager can also open a new account on the Charge screen with their PIN. The Gift cards, store credit and house accounts tab in the docs covers house accounts.