We got this cooker last year. I’ve not used it as much as hoped but a few thoughts.

There will always be some water loss to venting but I’d imagine that the electronic control in the modern electric ones does keep this to a minimum.

Veg are likely to cause a gain in water and I made a tasteless veg curry before finding this out. Two suggestions here are to look for recipes online aimed at these cookers. And again a combination of trial and error and experience. Be sure that you don’t go below the minimum level for your appliance.

Boiling dry isn’t a particular concern with a unit like ours. After cooking for a preset time, it will go into a “keep warm” mode. This drops the temperature to say 70 or 80% and should be OK for hours.