I think you're missing the point of a riser. I'd the motherboard only has a 3.0x1 port, plugging in an x16 riser means it'll still only be x1 electrically, but it can physically fit larger cards. If the back of the slot is open already there not much point of using a riser since you can physically fit larger cards already.
- If your board has pcie 3.0x1, you want the pcie 3.0 card. Running at 2.0x1 reduces speed by 50%
Probably depends on how much they tried to import. 1mg is probably no big deal, but 1Mg would be.