Mix local and cloud only users

One of my customer has an office in country A and some satellite users in country B. There is a AD server in country A, and users in county A office is using the AD for desktop login. Users in country B will not need to login to the network in country A.

Current email is G Suite (paid version), there is no local Exchange server.

Customer wants to move from G Suite to Office 365 and to sync local AD password to Office 365.

Can we only sync users password for country A between the local AD and Office 365, while users in country B will only manage their password via the webmail interface? Or I will need to create those country B users inside the AD server in country A?

Thanks.