What's certainly true is that if your instructor tells you that you are not to exceed 20 degrees AOB in the circuit then don't.
Well, I would ask why not.
I think there is some confusion on here between Angle of Bank and Angle of Attack. They are not the same thing.
That wings level "belly check" on base that Stik refers to is pretty important if you want to have a good look at what's happening on final. Also, the person who I think is one of the higest authorities on landing a Pitts doesn't actually teach a curving approach. He teaches a quick base leg where you check final, then to fly 'the line' to the numbers which actually tracks along the ground in a line. It might appear to be curved from the cockpit, but that's because he is constantly changing his side slip all the way down a final approach that is a few degress off the extended centreline. Well, that's what I think he is doing
What is most important is that everybody does the same thing. So mixing these "military" patterns up with a "civilian" pattern might not be the most sensible thing to do. If you are flying in the US at an uncontrolled civilian airfield and you fly a downwind then a final without a base leg in between, and you hit somebody and survive, the FAA will be more likely to violate you than the other guy. The AIM shows a base leg, and although it is advisory, you will get into trouble if you cause an accident by not following the advice.