Multiuser also is just one requirement in regard of how you work with data, if you want/need to lock records for example, depends on the need of the specific application. Many things also depend on the amount of data and number of users, hardware, LAN size, bandwidth and much more. There is no one size fits all answer on such a broad question.
It's not, that anything you can do for compatibility reasons only is there for compatibility reasons and there only is one best practice for any new application you do in VFP9, especially in regard to data access. Of course you should stop using screens @SAY/GET etc. and use Winforms, but you may or may not make use of OOP features, that's already a matter of taste.
You already had more specific questions, it would be ok to repeat them in this context, but maybe you don't want to aks them.
Bye, Olaf.