At the stroke of two external hard drives (Seagate 4Tb USB3.0) and an external sound card (RME Babyface) are always connected.
At the same time I use different, small 2.5 hard drives that are powered only by USB.
No problems with all this!
Even in the "worst case" scenario, where two 4TB Seagate communicate with each other (backup) and sound card is active, my external USB3.0 SSD is not really slower than when it is connected directly to the Macbook (connected according to the Xbench test, the Macbook : Score 267, the hub: 265 Score)
I am very satisfied with the device for two months.