The Xyber Hydra offers solid transfer speeds and expansive storage, but it takes some work to get up and running.
Switch My Slot is an Android app that helps you switch between android A & B slots easily without having to enter commands in adb or fastboot shell. You don't even need TWRP recovery to use it.
Before I had a home server or a home NAS, I used external hard drives for backup storage while keeping the most essential, need-to-have-access files in the cloud. Then I moved to mostly cloud storage ...