For the headsets, we don’t really look at use on the in headset browsers, as we concentrate on the native apps themselves.
However we can take a look to see if the experience on the headset browser can be improved, it just won’t ever be as good as using the app which gives you the full capabilities of the device.
For the second part of your question, the answer is, “it depends”. With your authoring licence, you get 250 named viewer licences, so if your client has a smaller number of people that want to take the content, you could have them take it as users in your organization. If they do get their own licence (which yes, does come with a minimum of one authoring licence but then can have as many users tied to it as you want), they can then take advantage of the analytics they get from their users as they take the experiences.