We have a hitch for your 2017 BMW X4, part # C13316, but it is a 2 inch hitch.
Normally this is the preferred hitch size when available, but what you can do is use the hitch reducer part # HT02 to reduce the hitch down to a 1-1/4 inch size and you'd be good. view full answer...
The only hitch we have for your 2015 BMW X4 is the Curt part # C13316 that you referenced which is a 2 inch hitch. We do have a reducer though that will allow you to reduce the hitch size down to the smaller 1-1/4 inch size as part # HT02. view full answer...
Yes we have the Yakima Fullback part # Y02634 which is a confirmed fit for your 2019 BMW X4. This is one of the nicest trunk racks around due to how easy it is to install and fact it comes with locks for the bike rack to the vehicle as well as for bikes to the rack. view full answer...
For your 2016 BMW X4 the best option for trailer wiring is the ZCI part # 119250KIT which instead of requiring you to splice into the vehicle uses sensors that clamp around the wires instead. view full answer...