Windows 10: USB 3.1 Gen 2 header

I'd like to add a USB 3.1 Gen 2 header to my computer, As the pic shows, the case is pretty open and mounting a header, if that is the right term, should be fairly easy.
The "front" of the case, where I sit, on the left.
I have looked around Google, found a few ideas, but wanted to tap into the experience here since it has always proven the best resource.




:)

 

Why is my USB 3.1 gen 2 adapter (USB C Female to USB A Male) causing bottlenecking?

I recently picked up an SSD and enclosure with a built in USB Cable. CrystalDiskMark shows a >500MB/s read speed and >400MB/s write speed with a direct USB C connection to a USB 3.1 gen 2 port, so all good here.

But I also picked up these adaptors from amazon.co.uk to ensure I could connect the drive to more common USB type A ports. These adapters noted that they could handle the 10Gbit speeds of USB 3.1 gen 2, although they do note that when this is the case the "other side" (Type A side) runs at USB 2 speeds. Out of a lack of options I decided to give them a go nonetheless and the claim is true. But it's not as simple as saying "these must really just be USB 2 adaptors with a blue finish".

When using the adapter to connect the drive to a front panel USB 3.1 gen 1 port connected to the USB 3 motherboard header, the speeds are ~300MB/s and 400MB/s read and write respectively. So the adapter can handle high throughput but just can't when used in gen 1 or 2 ports on the IO panel of the motherboard itself. Maybe this is a motherboard issue...

Edit: Just verified this across 2 Desktop systems:

• Rear Motherboard IO (USB 3.1 gen 1 and gen 2) with adapter: ~40BM/s
  R/W
  
• Rear Motherboard USB C with no adapter ~500MB/s R and ~400MB/s W
  (full speed)
  
• Front panel IO connected to motherboard USB 3 header (gen 1) with
  adapter ~200MB/s R ~400MB/s W
  

What am I missing here? I have found only one adapter available that clearly states it has 10Gbit ports at either end but it's pricey so any alternative suggestions are welcome. Notably, it has a significant rectangle shape at the USB C side, maybe this is part of the explanation...? See below:

 

Stupid Question - USB 2 Ports Into USB 3 Header?

So my old-ish case has 4 USB 2 ports in front. If I connected them to a USB 3 header on my motherboard, would they work? And if so, just at USB 2 speed right? I assume yes and yes, but I've only really worked with USB 2, and all I know is that all the plugs look the same, so I'm not familiar with these.

 

Stupid Question - USB 2 Ports Into USB 3 Header?

ensure to get the pinout on the USB 2 Connector and the Pinout on the USB 3.0 Header, USB 3.0 has additional Lines in it compared to USB 2.0/1.1/1.0