I'll try to pick the best options for what fits with a given character concept in a vacuum. Not purely optimized, and not a fluff bunny gimp. And depending on the table and setting I'll play it and tweak by ear. There might be something in the system that is incredibly easy to attain with significant gameplay value. But is not ubiquitous in the setting for narrative reasons, such as a cybernetic implant that is uncomfortable and is minorly deforming in a way that has no mechanical drawback. I won't take that unless it fits a really cyber heavy character, or unless the table is about super combat optimization. When in Rome and such.
I think the conversation in the last few pages is one I've seen before that basically comes down to interplay between game reality and rules abstraction. In real life we have only rough ideas of the competing efficacy of similar cartridges. Rough ideas don't work in mechanics. I view the hit dice as an abstraction of a general understanding. Bigger weapons are usually a bit better than smaller ones, people in the setting normally understand this, and yet for reasons matching those in real life their kits are usually not optimized. People fought with what they were trained with, what was popular, what was comfortable, and what they could afford. Sometimes you have professional armies where the kit is built around a macro based metagame, Romans and the gladius, Greeks and the spear. Sometimes you had a band of knights who wielded a bunch of different personal weapons, because they felt mre comfortable with them. Even though by the rules of 5e some of them were making suboptimal choices, because 5e in its simplicity(which I like fyi) doesn't bother to model the real life mechanical reasons why someone who is able to use a greatsword will always be better with a longsword. Maybe he's small, not small humanoid, but maybe he's like 5' 4" has smaller hands and thin frame. He knows how to use a greatsword, but it's uncomfortable, and he's slower with it. In some systems this would be modeled, it's not in this one. I don't think that the system makes those people stop existing, it doesn't make the small guy more effective because there is no favored weapon rule. It doesn't make him stupid because the system doesn't model a common real life issue.
If you feel like the abstraction is not just a general understanding distilled into gameplay, but empirical fact. Something that many primers and papers have been written about, and therefore 95% of warriors pick the best gear they can get proficiency in. That's okay, it's no crime just different strokes. It doesn't reflect our history, but neither does shrugging off an axe to the face, or people who can take 20 times the punishment of a healthy farmhand in martial combat. If you also believe that characters knowledge extends to seeing their companions class features and builds, and knowing that the fighter is an idiot for using a d6 weapon but the monk isn't. That's fine too. For some players getting rid of the body of a murder is a long drawn out affair, it's detailed, there's multiple rolls, chance encounters, and a serious chance of disaster. In some games they say "We dump him in the river," and the GM just nods. Whatever works at your table is fine, we don't all have to play the same way, and clearly that's for the best.