Yeah I understand. I've been lucky with AliExpress, but it's the Chinese eBay. So it could go either way depending on the seller. Most Tesla Accessory suppliers in the US sell the same Chinese products at a mark-up, but hopefully the better ones do a quality control before sending the items on.
Yes they do have metal clips and come with a roll of foam tape (see pictures attached). And the same metal centre-ring as original Tesla aero covers.
I've taken these aero covers on and off a quote a few times without issue. They clip on strongly and the plastic had no issues.
I'm getting as good efficiency as with stock ones. They come in Left & Right sides (mirror-imaged), which should help efficiency. Or at least they look better spinning the correct way each side.
And yeah, when on Mobile, the Aliexpress website doesn't seem to show the Contact Seller option. I had to select 'Desktop Site' (in my case Chrome browser on Adnroid), and then it shows the 'Sold By xyz Store' option halfway down the page. Then there is 'Contact Seller' on the next page. Or just use a PC - although I noticed my links above were for done on phone, and it's too late to edit. Here it is again for PC, where 'Message' is in the top right corner.