Only the X370 AsRock board is more expensive. Asrock also has a B350 version that is identical except for a slightly slower wifi card and is priced identically to the Gigabyte board.
www.newegg.com/Product/Product.aspx?Item=13-157-780
They have the same headers. USB 3.0 and USB 3.1 Gen 1 are the same connector. USB 3.0 was just rebranded as USB 3.1 Gen 1 (both are 5Gbps). I think you may be confusing 3.1 Gen 1 (5 Gbps) vs Gen 2 (10 Gbps).
No, the fins direct air in the same direction. Also, with the l9a, not even a custom bracket would be able to help as it is longer than the l9i to fill the rectangular keep out zone on amd boards.
Newegg has the AsRock AM4 ITX board listed as releasing next Friday. Up for pre-order in US for $160.
https://www.newegg.com/Product/Product.aspx?Item=N82E16813157779&FM=1
That monitor uses displayport over usb-c. That means it will only run off the iGPU of something like a MacBook or Windows device with a USB-C interface. It cannot connect to a dGPU.
EVGA's blower card doesn't have a backplate and a mostly plastic shroud. Performance and noise are pretty much the same.
EDIT: You could also buy the blower and a FE cooler off ebay. They're the same PCB and it might be the cheaper option.
Stumbled across this looking for whether the new bracket is available yet. Hopefully it will be available by mid-April when cases start shipping and ITX motherboards for Ryzen start becoming available.