Yes. You can create boards in Placker without exporting them to Trello.
Many teams prefer to keep their boards synced between Trello and Placker so that members that are used to Trello can continue updating their cards there. Also, there might be power-ups that you are currently using that are not supported by Placker.
However, Placker features like Gantt charts, card mirroring, reports, etc., are available in boards regardless if they are exported to Trello.