Find a local dealership. You'll pay a little more, but it'll be assembled and if the dealership is worth their salt, they will have also used Locktite on problem bolts. Despite the amazing progress in quality that Chinese bikes have come, apparently they haven't yet figured out that bolts aren't supposed to rattle.
Keep in mind that some of these companies will drop ship the bikes from the importer, so you may not receive your cert of origin until weeks after you get the bike. That's why I'd recommend finding a physical dealership nearby.
It looks like the majority of complaints from these sites are slow shipping of cert or origin and/or the shipper damaging the bike in transit.
While I do like the look of the Icebear more than the Grom, the $2k price tag puts it only a couple hundred dollars off a clean used real Grom. On Chicago's CL I've very recently seen two low mile Groms, one for $1,800 and another for $2,200. And if you only want to do wheelies and other stunts, get something cheap like a TaoTao Hellcat. A search of Grom forums seem to show that not even real Groms are fond of burnouts and wheelies with a number of blown engines as proof. But if you really want the Icebear, I say go for it! And please make videos and such because I do find Chinese bikes to be pretty interesting.
I have a Chinese 150cc scooter from 2008. The GY6 in the thing has been dormant for over a decade but a couple weeks ago I got it to fire after putting in a new carb. Now once I get my fuel issue fixed it'll become my "Mad Max Rat Rod" for the Gambler 500. I don't expect it to survive the rally and that's okay, I only spent about $200 on the thing.