Hi Iza,
There are two detection mechanisms in Marketing application:
Duplicate detection rules:
https://docs.microsoft.com/en-us/dynamics365/customer-engagement/marketing/business-management-settings#duplicate-detection-rules
Matching strategy:
https://docs.microsoft.com/en-us/dynamics365/customer-engagement/marketing/marketing-settings#configure-how-incoming-form-data-is-matched-to-existing-records
There are 2 ways to view all rules and disable Duplicate detection rules(could not distinguish lead from Marketing Form):
1.In Settings > Business management > Duplicate detection

2. In Advanced settings > Settings > System > Data Manament > Duplicate detection rules,
there are more rules than you can see in Marketing settings

The purpose of Duplicate detection rules is that when you create a new record from CRM, it will give user a popout notification, and you can ignore it to save the duplicate record.

You could see following guide for detailed Duplicate detection rules configuration:
https://crmbook.powerobjects.com/basics/data-management-in-microsoft-dynamics-crm/keeping-data-clean-in-microsoft-dynamics-crm/
While marketing page/form visitors' data creation and update are controlled by Matching strategy, not Duplicate detection rules.
You can find it in Settings > Marketing settings > Matching strategy

For Lead as example, if there was a lead record,
then if a visitor submits same email address data from same marketing page,
CRM will just update the record.

All submissions will be recorded, you can find it in Insights tab:

You could filter interested leads based on it.
However, this part of statistics couldn't be viewed as other entities records in CRM,
you should integrate Power BI to make more advanced analytics.
https://docs.microsoft.com/en-us/dynamics365/customer-engagement/marketing/custom-analytics
To make leads from marketing form without update, just add records per submission:
- Deactive default Lead Matching strategy

2. Create a custom new matching strategy and add Lean ID as attribute, because all records in CRM have unique id.
3(Important). Apply the strategy to our marketing form,
due to atributes(fields) that were added into matching strategy are required to be added on form,
we have to add leadid field to our form and set it as required, give it a default value and hide it.
Don't worry about this, because even if it has default value, but CRM won't process this data and will still generate unique id for newly created record.

Hope above would help.
Regards
Johnny