Is it possible to synchronize only the AD users members of defined AD groups in Nprinting?

Yes it possible, you will need to define your LDAP filters depending on your Active Directory structure. 

Example:

My company domain in "Domain.local"
All our users are stored in container with Distinguished Name CN=Users,DC=domain,DC=local
We have created a special Organizational Unit for NPrinting, with a container  in which we created all the following groups.

* NPrinting_Admins
Distinguished Name: CN=NPrinting_Admins,OU=NPrinting,OU=Qlik,DC=domain,DC=local
* Nprinting_BI_Users
Distinguished Name:  CN=Nprinting_BI_Users,OU=NPrinting,OU=Qlik,DC=domain,DC=local
* NPrinting_Developers
Distinguished Name: CN=NPrinting_Developers,OU=NPrinting,OU=Qlik,DC=domain,DC=local
* NPrinting_VIP_Users
Distinguished Name:  CN=NPrinting_VIP_Users,OU=NPrinting,OU=Qlik,DC=domain,DC=local

We would like to import in NPrinting only the users members of these groups. 

We have been able to do it with the following settings :

** Connection path : ldap://domain.local/
** Entry attributes > User identification > change to "user"
**Additionnal user filters

(&(objectCategory=Person)(sAMAccountName=*)(|(memberof=CN=CN=NPrinting_Admins,OU=NPrinting,OU=Qlik,DC=domain,DC=local)(memberof=CN=Nprinting_BI_Users,OU=NPrinting,OU=Qlik,DC=domain,DC=local)(memberof=CN=NPrinting_Developers,OU=NPrinting,OU=Qlik,DC=domain,DC=local)(memberof=CN=NPrinting_VIP_Users,OU=NPrinting,OU=Qlik,DC=domain,DC=local)))

** Additionnal group filter 

(&(objectCategory=group)(name=*NPrinting*))

More information on LDAP filters:

https://confluence.atlassian.com/kb/how-to-write-ldap-search-filters-792496933.html
https://social.technet.microsoft.com/wiki/contents/articles/5392.active-directory-ldap-syntax-filters.aspx?PageIndex=2