Ok. Did some more testing. Enough so that I can render some more opinions...
First, I want to talk about these earbuds and full-face helmets. Are they full-face helmet friendly? In a word - no. Not in my opinion. It's just too difficult to get the helmet on over these earbuds without dislodging them enough to impact their performance. Even if you get lucky, I believe their noise reduction capability is just not sufficient. Hearing conservation is a priority and I don't think this kit is up to the task - at least with a full-face helmet.
How about the half helmet? Do they get it done with those? I would say that it depends. I installed the ear pads I mentioned in my previous post...

The end result on my '18 Heritage with half helmet and ear pads installed? Acceptable. In fact pretty good overall. Wind noise and hearing conservation/noise reduction was actually pretty decent. Sound quality of music and podcast was quite good. Volume did not need to be turned up to overcome ambient noise. The combination of the windshield on the Heritage and the installed ear pads were key to these results.
So I wanted to present a more significant challenge... One which I didn't really expect the Motikom kit to be able to meet. Here it is... The Nightster...

Was I pleasantly surprised? Nope. As expected, the Nightster did this kit in.
Two challenges here... The direct wind blast and the Vance & Hines Sideshots. Even if the bike had the OEM exhaust still installed, the direct wind blast and resulting wind noise would prove to be just too much (even with the ear pads installed) for the Motikom unit. This bike also presents an additional challenge to full-face helmets. The Sideshots location etc. turns the full-face helmet into an echo chamber. Actual ear plugs with a NRR of 33 work well enough on this bike, but I doubt much else ever will.
Long term wear/comfort? Can these earbuds be worn all day? I don't know. I don't think they are too bad as far as earbuds go. But they are not as comfortable as the Hearos. The ear pads do press against the earbuds a smidgen, impacting overall comfort. I would say it depends on the individual. I probably could wear them a couple hours at a time without too much problem. But time will tell.
Controls... I would say the knobs and buttons are acceptable. However, I have to imagine that the controls on a Sena or Cardo are probably easier to work with (see button locations on the Motikom in relation to earbud wires and think gloved hands). Plus, the function of the knobs and buttons are probably more complicated and harder to remember on the Motikom as compared to something like the Sena or Cardos. I can't say this for certain, because I haven't used either a Sena or Cardo. But, on the surface the Sena/Cardos controls look like they might be easier to figure out and use.
Where to go from here? Well first... Let me say I'm not sold on listening to music or podcast while riding. To me, I find it a bit distracting and I get a feeling of being a bit disconnected from the bike, the environment, and what I'm doing. Plus, music is not that big of a thing with me that it has to be apart of everything that I do. In fact, I don't listen to music that much at all these days.
Navigation... Do I need audio directions/prompts from my Nav setup? Nope. Not at all. In fact, I generally have them turned off in my car (let alone the bike). The only Nav audio prompts I generally have enabled are Waze Alerts. I don't use Waze on the bike - so Nav audio is not needed.
What about phone calls? Sure... there might be an occasion where I'd want to take or make a call while on the bike. But I think it would be pretty rare.
Part of the pleasure of riding a bike is to get away from it all. This all seems counterproductive.
My wife on the other hand says she would like to listen to music while we ride and have to ability to more easily talk to me (she wants an intercom). So we must make the boss happy.
In the end... And has been mentioned... I believe that custom molded/fitted earbuds like these might be the best way to go....
inearz sport UH-2 STEREO custom fitted earbuds

But man... Are those things pricey or what?
Silicone - $329
Acrylic - $515
Fusionsoft - $750
Plus there's the cost of getting the ear molds made by the audiologist etc.
However, if this is a serious need/want, it might be worth it to get a pair of the Inearz earbuds and use them with a Sena/Cardo. The Inearz earbuds have a 29-32 dba noise reduction spec. So, they might check all the boxes... Hearing conservation (no matter the bike, helmet etc.), full-face helmet friendliness, sound quality, all day comfort(?) etc.
I talked to Inearz about the difference in the materials used. They said the silicone might be more comfortable for some, but that one's sweat and oils will tend to break them down over time. It might be more cost effective long term to get the acrylic.
Overall... I believe I'll need to do some more experimenting with the wife to determine just how desirable/necessary an intercom is (and her ability to listen to music) in the long run before I would consider the total cost of a system that would be needed to fill the bill (Inearz earbuds for both of us, Cardos for both of us, etc.). In the interim, the Motikom units might suffice to facilitate this experimentation.
Would I recommend the Motikoms in the end? Maybe... But only for limited use cases.