Function backed link type traverse export and the linked user name property

Is it possible to traverse link types and retrieve properties from multiple object types.
Currently, I have a function which does this. But I only select fixed properties from the link type. And from the original object type I select it based on the properties visible in the object table widget. But the problem here is, since I have a linked type and almost ~1M objects reside on the original object type, it is impossible to have this export. Is there a way I can get pass the limitation.
I think the threshold I hit for now is ~50mb before the download fails. Is there an alternative way to achieve this. Or what exactly is the limit?

And the next question is -
There is a linked object property, which is a user name. But when export is success this field appears to be the user id instead. How do I resolve this?

Answer for your 2nd question -
From OMA for the username property add type classes as “multipass:user_id”

Now in table widget toggle option to resolve user ids.

Still, I found an issue here as this option is placed under CSV export menu, so resolve user ids is working fine for CSV export only and not Excel export (maybe it will be fixed soon).