I have tried the first option: Export Ruleset, and it works. However, my application is built on mutliple rulesets and I have to make multiple exports for the different rulesets. This method is quick though and it can be good for small fixes, but not in general for migrating the application.
For the second point, I need to check where I can find details to try it out and what exactly it does. Does this allow to package multiple rulesets.
The thing is that on the grid, it displays the .pySelected property of the user that has a value of True by default. Meaning that if we add some filter we still have this property checked and I am afraid that when pressing the Next it would take these even if not visible on the grid.
I have tried one thing to have 1000 users per page which works nicely, and now I have only 3 pages. So this works too, and is a cool solution.