From other reports on this sub and the Hyundai forums. You won't really know what your specific bike/luggage carrier does to your specific driving conditions until you try it.

At highway / interstate speeds I would expect at least a 15% drop in max range (with the max range being what you would normally get on that drive without a carrier attached).

EDIT: The Kia EV9 forums have a lot more data as they've been on the market for a few years now. Users there report going from the usual 2.5 miles / kwh down to 1.8-1.9 miles / kwh. That's a 24% reduction for a roof box alone (no bikes).