If I use Storage Expansion card on Xbox Series will my USB storages be active/work?

it's completely separate, and yes on PC you can either use the slot or the SSD because they're sharing lanes

Your biggest problem potentially with your USB devices is going to be power on the bus, I highly recommend that if they do not already have external power supplies that you can get a powered hub to plug them into

Hi,

Both Series X/S games and Xbox One games that been optimised (I'm British) for Series X/S must be installed on either the internal storage or the expansion card. They can not be run from a USB connected storage device. My optimised Series X/S Xbox One games
were moved to my Expansion card during their update.

Xbox Series X|S games can not be run from USB storage devices. These drives are too slow for Series X|S games, regardless of them being on Game Pass or not.

Series X|S games can only be played on either the Internal SSD, a Seagate Storage Expansion Card for Xbox Series X|S or the WD_BLACK C50 Expansion Card for Xbox

You can use the same drives and the same games

You cannot install Series games on a USB hard drive, only the internal storage and the expansion cards

Hi H0MiiCiiDE, my name is Rodrigo. I'm an Independent Advisor and a member of the Microsoft community and I'd love to assist you today.

I am sorry but the Expansion card won't work for that.

I am not sure why it said to connect it to a PC, since it is not possible.

"Will this card work on my Xbox One or PC?

No. The Storage Expansion Card works exclusively with the Xbox Series X|S console for optimized compatibility and gameplay performance. "

For more information: https://www.seagate.com/products/gaming-drives/xbox-gaming/storage-expansion-for-xbox-series-x/faq/