Secure Access from external source to User Specific Data

Hey everyone.

I am currently working on an application where you have two possible ways of accessing a specific visitor customized page:

• via owning a fully verified user account and logging in
• via a signed link, you'll receive as guest user

Since it is about personal data and I want customers to be able to checkout as guests, I am wondering what the "most secure" way for guests is.

Is a temporary signed route via E-Mail enough?

I am open for suggestions, maybe someone else had the same question before.