that only being able to queue up to 2 jobs at a time
These make it look like there is a bunch of extra development we need to do to load our users with things like polling for jobs that complete, submit new ones etc.
It is not clear to me whether the import/export extension can help with this or indeed what benefit it provides? Can we give it all our users and will it take care of submitting and polling jobs?
So in summary, my questions are:
Q1) What benefit does the extension provide and should we use that?
Q2) Are there any tools/projects available that would take care of this one-time activity?
You are correct regarding the User Import limitations, these do apply to the Import/Export extension as well. I believe it can be argues that the extension is more user-friendly, compared to creating Jobs with the Management API, but the same limitations apply here as well.
The amount of users that can be imported/job does vary depending on the amount of attributes the users have and if the password hashes also need to be imported. Based on this, you can make a rough estimate of how many Import jobs it would take to complete all the users.
One exception to take into consideration is that Enterprise subscription customers may have a main production tenant upgraded to a higher tier to increase bulk import throughput during a large production migration only. This is only eligible for production tenants and production migration use cases. If this applies to you, a conversation with your TAM might help plan out the migration and streamline the process
I believe that, in order to upgrade the main production tenant for a one-time migration, a Support case will need to be opened and our team will be able to make the necessary changes to support this.
There isn’t a specific way of overcoming the 500kb and 2 simultaneous jobs limits, but there could be a way to speed up this process for rare, large migrations such as the one you are facing.