I don't think we have to create any account. They should be sending us an email with a zoom link that we just have to click and log in. When is your ceremony btw?
I think the app is better, but that’s up to you. But if you would like to try see how it works it’s free to create a zoom account and you can make your own meeting and invite a friend to test your sound and video on it.
If you don’t want to create a zoom account, ask a friend to do it and invite you to a test meeting, that might help you feel more comfortable in advance. But if your oath is early tomorrow you might not have time before the ceremony.