Containers and return values

hi guys! i've got two little troubles (i'm new at qt, be nice with me :D):
1) is there a widget that allows to contain other widget with access by that? i mean, for example:
ui->myContainer->myLabel.text = "hello";
and not:
ui->myLabel.text = "hello";
2) i can't understand why, for example, in a doubleSpinBox, value() return double, and not qreal (i know that in a x86 cpu qreal is double, but what happen when i run my app on an arm cpu, where qreal is float 'couse double don't exist?)
thanks :)