How the system works (UI) Registration Form > Redirect to Another Page with Products (based on the submitted in the registration form)

(backend) API will check the validity > Valid or not it will push to database > Only Valid will be recorded in our CRM (salesforce)

When testing this manually, we would just usually do it in one flow: Register > Check Redirected in Products Page > Check in Database > Check in CRM

However, in Automated Test, I think of two options right now

a. One Test (like manual) - this is fastest

b. Multiple Separate Test - slower, but easier to identify where the test has failed

Is there an option C? And how would you organise it?

Most of the things I find online are always "IT DEPENDS" or the sample projects I find are too small (only login).

(I'm just starting with automation. Automating is easy but as the Automation Tests are getting bigger and a lot of tests need to be refactored, structures need to be fixed, hierarchy, not sure what to do really)