How can I change this: when users get the result from a form, the email sender they see is this: [email protected] This is not customer friendly. Can I get my own email address in here somehow?

If you don't want to receive email through FormNX SMTP then you can add your own STMP settings and use that email SMTP to send emails.
Please check out this documentation: https://formnx.com/details/docs/features/email-... to know how you can add your own email SMTP settings and choose that email SMTP to send email notifications