Let's look at your switches...
/E - not needed because you have /mir
/ZB - restartable mode, shouldn't hurt, don't think I ever used it.
/COPYALL - ok
/MIR - ok
/R:0 - ok, but you will need to examine why the copy failed and fix it.
/W:0 - not needed because /r:0 doesn't retry
/V - depends on how many millions of files you have in the folders
/TEE - ok
/log - ok
Copyall will copy the NTFS permissions. That will work for AD groups and users and builtin security principals like the Administrators group. But if your source folder references local groups then on the destination server you will see a dead SID in the folder permissions.
Start small and test with a limited number of folders. The first time that you run it, the files will be copied. The next time you run it (the exact same command) it should run very fast because the /mir switch will recognize that the destination folder already contains the files/folders and there is nothing to do.
When you are ready to cut over the users, either remove the share or change the share permissions to read only so that users can't update the source folders.