there are no options in Garmin Express to set a upper limit for the download speed, which is a bit annoying when you want to update devices in the background
it fully saturates my 100Mbit connection. It sometimes dips a bit if the transfer rate can't keep up. so maybe, at least for some, the limiting factor is the decompression (probably CPU), memory or USB-port. Or I just get lucky
Well the ones that come here do but as they keep being told 99% of the time it's a problem within their system somewhere. Most of Garmin users have no problem at all.