flarum/pusher is a 1st party extension from the flarum project team that incorporates some realtime features using the Pusher.com provided websocket service. It has limited functionality, it scales well but requires a subscription, it requires hardly any set up aside from the pusher.com account.
blomstra/realtime is an extension I wrote (disclaimer) as part of the company I co-founded (Blomstra). Realtime is developed by people also part of the core team. It offers more functionality than the Pusher extension and integrates with more extensions. To use it you need to be on a plan on Extiverse:
- for non-profit communities you can choose a lifetime license which does not offer installation support,
- for non- and for-profit communities you can choose a subscription that does offer installation support.
With Realtime you set up your own websocket service on your server, so there's no limit to how many users it can process aside from the capacity of your server. As such there are no additional costs aside from the selected plan, no matter how successful your community is.
I hope this helps, let me know if you have any questions.
