What version of USB is the Fenix 6x compatible with?

with Garmin Connect. 

USB

? ? 
Garmin Express. Not Garmin Connect : 

www.garmin.com/.../

I'm wondering if it matters what port I connect the watch to update with Garmin Connect.  I couldn't find any description of the usb version that the watch supports.

If your computer has a USB port that accepts the USB connector on the charging cable that came with your watch, then you are good to go.

HTH

Any USB-Port from 2.0 upwards.

Yes, I understand it connects. I'm wondering if there is a spec that states which exact version of usb the watch supports, and if it makes a difference in connection speed.  The map transfer between my watch and computer is much slower than the download from the internet.

Yes, I understand it connects. I'm wondering if there is a spec that states which exact version of usb the watch supports, and if it makes a difference in connection speed.  The map transfer between my watch and computer is much slower than the download from the internet.

The bottleneck is the speed of the flash memory. USB 2.0 is up to 480MBit/s in reality it is about 35 Mbyte/s. And that is for sure faster than the flash in the Watch. So you don't need to know if the Watch supports USB 3.2 - it won't make it quicker.

Does it state that anywhere in a manual or webpage specification?

That makes sense.  I'm a little annoyed I couldn't find a version stated anywhere.  Is it 1.1, 2.0, etc?

Thanks!

I just checked with "USB Device Tree Viewer". The 6X connects at an USB 3.0 port with USB 2.0. Like I said: It won't differ if you connect it to USB 2.0, 3.0, 3.1 or 3.2.