They should sort out the pulling under braking before you get the car, put it in writing now so they can not deny knowing.
Easy to check if its uneven, park on level
surface then measure from centre of wheel to wheel arch on both sides.
My first idea would be tyre pressure as its pulling in the direction that has a lean.
I tend to get the cars checked for alignment each spring,on a Hunter rig
www.alignmycar.co.uk.it does all four wheels , its surprising how they get knocked driving from pot hole to pot hole.Saves uneven tyre wear.
If any trouble does develope you have a good BMW warranty, but if concerned ask to see the check that car has not been involved in serious accident. They should have that check already done.
Don't anticipate the dealer will get it all correct before you get the car. The Audi A1 for our grand daughter was delivered in absolutly perfect condition , inside and outside,the engine bay was spotless,levels all correct and 3/4 tank of petrol. BUT they let themselves down ,tyre pressures were all 1.6bar should be 2.3/2.2 bar