It's not a hardware issue. The USB hardware already demonstrates it can attain high bandwidth (transfer speeds) when using a single connected USB device.
It's a software issue. Once the USB drivers are properly enumerated they pass control onto the (Windows) OS. Anyone who's ever copied files/folders in Windows knows how terrible this can be. Multiple simultaneous transfers divide speed up into ever-diminishing slices of bandwidth, and the WinOS doesn't recover them (re-allocate "free" bandwidth) properly once one transfer has been completed. I call it "bad software multiplexing", an engineering joke (which is, admittedly, not very funny anyhow).
TL;DR version: don't blame ASUS for this one, blame Microsoft.
When your USB devices are all plugged into the USB ports, click through all your Windows Device Manager properties. You'll have options which allow you to balance Power and Bandwidth allocations - although they're somewhat limited and not very useful outside of optimizing very specific tasks on very specific configurations - still, you might find them useful.
Don't "Cut&Paste" when you can "Copy&Paste". Windows handles queued instructions poorly, it will take geometrically longer to Cut&Paste files than it would take you to manually Copy files then Delete files. Don't move ten folders or do things on ten drives all at once when you can do them one folder or one drive at a time - unless you plan to let Windows take charge and take forever to do what can (should) be accomplished in a fraction of the time.
You can try other file managers, file shells, and USB softwares which all promise to accelerate such mundane chores. I've never bothered - mostly because these things are typically commercial software which won't work until you buy them and, well, because there's so many utterly free linux versions available which already handle such multi-USB multi-drive multi-folder transfers quite efficiently, lol.
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