I think that protein level might have a little to do with body and head retention, but I think that beta-glucans have a bigger effect on head building and retention. Beta-glucans are polysaccharides that form long chains. The number one contributor of beta-glucan in brewing is raw barley. That level is reduced by a factor of ten when the barley is malted. I recall that raw wheat only has about 20 to 30 percent of the beta glucan production as raw barley. That does place raw wheat higher in beta-glucan than malted barley. I don't know how the beta-glucan content of malted wheat compares to raw, but I expect that it would be similar to malted barley. By the way, flaked grain is roughly equivalent to the raw product with respect to beta-glucan content.
I have brewed a bunch of beers with flaked barley in the past year. My last beer was a Dunkel with 1% flaked barley. The head was phenominal and long-lasting. But in this relatively clean beer, there was a somewhat worty or raw flavor that I feel came from the flaked barley. I won't be doing that again. In retrospect, even the ales that I brewed with flaked barley had a hint of that worty, raw flavor that I could plainly discern in the Dunkel, so flaked barley does have to be used sparingly in most beers. I think the reason it is successful in some stouts is that the roast flavors obscure or meld with that flaked barley flavor and add to the overall experience.
If I consider head and body builders again, it will likely be flaked wheat since I find its flavor crisper. The fact that it contributes far less beta-glucan would make it easier to dial in an appropriate level in the grist. PS: that 1% addition in the Dunkel was less than 2 oz. I'd have to wave just the bag over the mash tun to do much less!
I note that there is a mention of Chit Malt in some German brewing circles. That is very slightly malted barley that has just 'chitted' its rootlet out of the kernel. Since the level of modification would affect the beta-glucan content, I have to assume that Chit malt has some intermediate beta-glucan content.
I do recommend experimentation with flaked barley and wheat for building body and head. It is very effective. You do need to moderate their percentage when the beer flavor is more delicate. In addition, producing a huge head is not a good idea since you end up with a big pour of foam no matter what you do. So, maybe a 1/2% of flaked barley or 2% flaked wheat might be upper limits for their usage.