They are more aerobatic than you might think.
Dihedral? The planes you are considering are RTF or ARF I believe, in any case the dihedral is already built into the wing and should stay there while you are training.
You can always buy an extra wing later and take some of the dihedral out. The root rib is angled, that is where you get the dihedral.
Along with a dihedral brace that goes between the two wing halfs.
You will see what I mean when you assemble your trainer.