Can an iMac Pro drive 2x LG UltraFine 5K displays AND a Thunderbolt 3 or USB-C external drive?

I'd like to connect an iMac Pro with 2x 5k displays and external Thunderbolt 3 or USB-C storage. Is this possible?

I've been reading it's important to put each of the 5k displays on a different bus. Not sure if that implies there might be bandwidth issues or some other limitation in connecting an external hard drive to the same bus as one of the 5k displays (since both would be in use).