Account Merge / Link, how does it work?

hello, i was wondering if someone can explain me how the new Account Merge feature works

i have my A account with 3 characters
i have my B account with 9 characters, i want to merge it to A:

7 characters from B will move to A, but HOW i choose which one?

then, the remaining 2 characters on B will stay on B account or go to a new C account? may i choose which one to leave there and not to merge?

thank you very much for any coming help

ignore that feature, you can not use it and it does not work in that way.

That feature is only for players who had more than 10 characters on Deathwing + Ragnaros durign the merge

ah, dammit! okey, thanks