Manage Users:
1. Create and edit users in specified roles and all subordinate roles. User editing tasks include resetting passwords, setting quotas, creating default opportunity teams, and creating personal groups for those users
2. Unlock users
3. Assign users to specified profiles and permission sets
4. Create public groups and manage membership in specified public groups
5. Log in as users who have granted login access to their administrator
Manage custom objects:
1. Fields, Page Layouts and Record Types
2. Validation Rules
3. Custom Tabs
When delegating administration, keep the following in mind. Delegated administrators:
1. Can’t assign profiles or permission sets with the “Modify All Data” permission
2. Don’t see the None Specified option when selecting a role for new users
3. Need access to custom objects to access the merge fields on those objects from formulas
4.Can’t modify permission sets
5. A delegated administration group is a group of users who have the same admin privileges. These groups are not related to public groups used for sharing
To Setup, Delegated Administration, check the below link
https://www.infallibletechie.com/2018/10/how-to-setup-delegated-administration.html