I have a friend that needs some tire advice and was wondering if you guys can help me

he has a 2003 x5 4.4 and he is getting some 20x9.5 and 20x10.5.

He wants 50 series tire, is that too big? what size do you guys recommend? i was thinking 285/50/20 and 300/50/20. can somone give me some advice please?

thanks