Outside Mounted Blinds Curtain Rod Attachment (Black)

can I use double curtain rods

The ad says shipping is $3.75 yet when I check out the shipping has jumped to $20.15. Why is that?

Do these leave enough room to fully open (perpendicular to the window) the blind slats behind the curtain without touching the curtain?

There is a vid showing the bracket sliding on from the front XL ver. the product pics show it sliding down over the top.Is that a different product?