Hi & welcome to the community 
The old way of doing things had many things tied together, and you’d always needed to edit the host notification contacts. The new way of doing things is to not edit the host anymore, but dynamically apply notifications combined with users and groups.
You can also leverage certain things into notification templates, meaning to say you can group users into a usergroup, then assign this to a template with a context specific name, and then import that into your notification apply rule.
I would be that your 4 users can be grouped into something like “production-users”, “dev-users”, or similar.
If you cannot achieve the timeperiod filters on the notification object level, you can set such in the user object itself unless I am mistaken (Icinga 2 allows that).
That’s a common thing when working with Icinga 2, for any apply rule you’ll create and you cannot match the host name, or any oh the host’s attributes being available.
I’d advise to have a read into the monitoring basics and principles before going deep into the actual configuration. You’ll need to understand the object relations and specific differences, also when coming from the old world.
I don’t know if the Director has such a view, but users asked for this quite often - you can do that via REST API scripts, e.g. Filter hosts/services
Cheers,
Michael