The "parabolic bracing" notion seems to refer to the lengthwise section, and not the crosswise section. I think you are splitting hairs in the wrong part of your career  unless you have already built a bunch of classicals and exhausted all other fine detail.
The normal shaping lengthwise is to carve or plane a certain flat taper, which is more or less straight even if it might look somewhat parabolic. Usually the back taper stops at the bridge tieblock end, while the front taper is pretty short, 1-2 cm, unless you are in the "thick-in-front of-the-bridge" camp, and then you might want this taper to reach more or a lot more towards the bridge.
The crosswise section is usually triangular or rounded. The triangular ones are of course a little more efficient in stiffness per weight, but that does not necessarily make them better.
Same with the width of the braces. The 7mm width is old school. It's the width used religiously by Torres, and those who followed him before WW2. They are flat around 3mm and can be quite stiff especially if made round instead of triangular. More recent builders have gradually made the braces more narrow and taller. These are of course stiffer at the same weight. The small footprint is enough to keep it glued, and some might be even only 3.5mm in width (see Bream's 73 Romanillos)
On the other hand, I think that the old style braces have the advantage of crossing more grain and coupling better - I think they are able to keep the doming better if your thing is a deep dome.
Ruck, a famous builder, took wide braces to extreme even, replacing 3 of the 7 braces with wide veneer patches.
Romanillos have used several schemes, for example the widths and heights decreasing from 6.5mm for the center brace down to 4.5mm. all this is useless blabla unless you actually try it, and match the graduating stiffness of the braces to the graduating (or not) thickness of the top. I also found that it is important to find a certain balance between the two halves of the top.
The best thing you can do is not to overthink, but maybe pick a design you like the sound of, build several guitars, get the hang of it...Keep thinking, sure, but don't do it too much without actually building smth. It is so easy to lose control.
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