Hey Pierre,
Welcome to our support forums and thank you for choosing Event Tickets Plus! After some testing to make sure I’m providing correct information, let me try and break down how it works…
If you have the ‘Try to set the status of new ticket orders to “complete” automatically’ box checked under Events > Settings > Tickets (see screenshot below), WooCommerce will mark every order as ‘Complete’ – whether it be an electronic payment or via a written check.

If you don’t have the ‘Try to set the status of new ticket orders to “complete” automatically’ box checked, electronic payment orders will be marked as ‘Pending Payment’ status until you manually confirm the payment through WooCommerce and check payments will be marked as ‘On Hold’.
I hope this clarifies how the plugin works and if you feel it needs any improvements, our ears are to the ground over at our UserVoice Feature Ideas page. Let me know if you have any questions or comments and have a great evening. Cheers!