I'll address this in two sections, since password policies are handled differently than most other GPO settings.
For example, i need to know how many users has the strong password policy applied and i can't access computer by computer to check it.
If you're not using Fine Grained Password Policies, then all of your users will have the same password policy.
If you are using Fine Grained Password Policies, then you have to define a specific user or group to apply that policy to, so just count who is in that group.
You can use a combination of
Measure-Object in PowerShell if there are too many to count by hand or you want to automate it, for some reason.
Is there any way to get the number of users on an Active Directory with a specific Group policy applied?
Group policies apply to users or computers and are linked to domains, sites, and OUs. Simple check where the the policy that you're curious about is linked to, and then count everything that it applies to within that domain, site, or OU. The
Measure-Object PowerShell cmdlet is your friend here.