Yes, the plugin works well. It does not interfere with pages built with Elementor, so you can use both plugins on your site without any issues.
Your customers will be able to see the status of each of their orders from their My account page and, of course, you can show the status you prefer, such as assembling if you have created it and set it in the plugin.
Yes, you can select the orders and set them with the same status through bulk actions.
Yes, the email is sent when the order goes into that specific status. You have to configure the email that will be generated for that custom status, which includes a specific option for the custom email address. You can read more about the Email Settings in this page.
Yes, when you configure a new order status you can enable the option “Display in reports” from the Extra options section, as you can see here. Once enabled, you can include all the orders with the configured status in WooCommerce reports.
If you delete a custom order status and there are orders set in that status, they will be no longer visible but not deleted. Therefore, before deleting a status, we recommend checking if they are linked to some orders and possibly change them into a different status.