putting in a 5 degree difference from 45 to 50 on the cap iron edge isn't going to change your life, I tried it and it did nothing at all, no improvement, also tried 55 degrees, again no improvement compared to 45, I don't get it.
The ideal shape for a cap iron is rounded and not a flat facet. Stanley's cap iron is pretty close. If you condition the cap iron and hone/polish the leading edge, you end up with a tiny area that's very steep and then a varying angle after that.
I also would not be able to tell much between 50 vs. 55 flat, etc. The difference between a big flat facet at 50 vs. 80 though is drastic, and 80 in a large facet is very undesirable. It's better suited to a machine where the cut depth never changes and there's a jig to set a knife - like the supersurfacer.
We apparently like to make things difficult. To get an ideal setup with a cap iron, you round, hone the edge to clean it up and get it crisp and that's it. Some level of polish where the shaving meets the cap iron is also beneficial. I think I typically spend less than 2 minutes preparing the cap iron on an older wooden plane or double iron set. Same with stanley planes. hone and rotate the bevel of the cap iron a little bit terminating the stroke with relative steepness (subjectively 60 degrees or so, it'll always end up a little more) and then buff off the wire edge that results after thinning it a little bit. A deburring wheel followed by a buffer is also nice because very few cap irons (except some japanese) are fully hardened, and the deburr/buff deals with the wire edge pretty easily. Just don't buff a leading edge enough to round it over and under so that it will trap a shaving.
I tested all of these things A/B (comparing them) on a stanley style plane (a millers falls 9) and on a japanese plane. I found, without reading anything, that the rounded profile worked the best.
A poster on another forum mentioned when I stated that that nicholson says the same thing, which was the first I heard of nicholson. Nicholson's guidance for dimensioning and planing is superb, but it's a little sparse for beginners, I guess. Nicholson is also intention on matching the cap iron to the iron profile (camber) which I haven't seen the benefit to unless the sole follows the camber (like a gutter plane), but there's no harm to it.
when I tested the 80 degree flat wall, the cap iron becomes very difficult to set - going from being ineffective to too much resistance in a short span. The original supersurfacer video showed some preference for that, but the supersurfacer machines come with a precise setting jig so it doesn't matter if it's hard to set. The jig nails it. The university who did the study also stated flatly that the video was for a planing machine and not for hand tools - they released a separate paper for setting hand tools and it's kind of wishy washy and short. In that, they just more or less said that a shaving that shortens shows when the cap iron is set properly. I think they wanted to be able to provide something paint by number in setting the cap looking at it rather than observing the influence. a "shorter" shaving is their term for one that's become straight or is not curled because the action of the cap iron that straightens the shaving is compression and when someone sent me that paper, I was surprised (and confused) to see what they meant by the shaving being shorter. To say that the shaving straightens or parts of it will straighten once the cap iron is compressing the shavings would've been easier to understand, but the shavings are actually shorter if you measure them.
They do not actually need to be straight for tearout mitigation to occur and as time goes on, the more wood you dimension, the more you'll favor as little as possible - some observation of that the shaving is straightening if the shaving stays continuous.
Accurate and efficient dimensioning can't be had if there's significant tearout discontinuous shavings - once you get past jack work if you have a surface like that, you just create a huge series of intermittent cuts. Intermittent cuts dull an iron faster and require a series of starting and stopping. It's easier to stay in a cut than it is to initiate one. Not to mention, if you have some % of tearout even starting on a flat surface, you're already removing that % less from the start.
So, what's better about the very initial part of the cap being rounded instead of flat? you get better performance in terms of planing effort as you increase shaving thickness. As in, the same amount of tearout control can be had with less resistance.
If I just absolutely wasn't comfortable with rounding the tip, 50 to 60 degrees or so would be my choice for a flat facet and don't make the flat facet any bigger than it needs to be to control tearout. Making it taller just increases resistance on thicker shavings.