Based on cars I've seen in So. FL, dealers seems to order most of them with Premium Pkg. I did have a F30 328i service loaner the other day that did not have Premium, but it also didn't have sport seats. Seats were reasonably comfortable. I didn't notice anything troubling with comfort.
Consider looking for a car without sport seats and compare lumbar to no lumbar. Should give you a fairly decent idea of what to expect. You may need to ask dealer to check service loaners to find a basic car with no lumbar.