Explanation
To display only the proper lead sources based on the product category chosen, an administrator should create a dependency between the Product Category field and Lead Source field on Lead object. A dependency is a relationship between two picklist fields that restricts the values available in one picklist based on the value selected in another picklist. For example, an administrator can create a dependency that shows only Online Store and Social Media as lead sources if Product Category is Shoes, but shows only Trade Show and Magazine as lead sources if Product Category is Apparel. Creating a page layout for each category, creating business processes and record types for each category, or creating a single business process with record types for each category will not display only the proper lead sources based on the product category chosen.
References: https://help.salesforce.com/s/articleView?id=sf.customize_dependent.htm&type=5

Explanation
Permission sets are used to grant additional permissions and access settings to individual users without changing their profiles or requiring a new profile to be created. You can use permission sets to extend users' functional access without changing their existing profiles. To meet the request of giving comprehensive edit access on Campaigns to a few marketing users who have read-only access by default, you need to create a permission set with edit access on Campaigns and assign it to those users. References:
https://help.salesforce.com/s/articleView?id=sf.perm_sets_overview.htm&type=5

Explanation
Record types allow you to update the options in a picklist based on the kind of opportunity.
References: https://help.salesforce.com/s/articleView?id=sf.customize_recordtype.htm&type=5