The "Starfire" scifi series makes a good pass at answering this question.
Mating between mammals is always social and offspring are in the norm cared for by the parent. Ergo the vast majority of mammalian solo hunters are social when needs be.
The ability to communicate consistently changes many things.
The evolution of 'greater than animal' intelligence means that said animal becomes able to predict abstracted outcomes from known and speculated situations and choose to alter their behavior accordingly. It follows then that it can be shaped in any way it's reason and circumstances moves it.
I'd propose that it would take (a lot) longer for such a species to develop verbose language, being as the first requisite for language is the ability for signals to be understood and that (normally) requires repetition of particular consistent signals (unless telepathy) which clearly becomes less likely with less exposure to other individuals.
In fantasy and science fiction most authors (in my experience) opt for 'stoic and honorable' when 'uplifting' such species, the reasoning (when given) being much-like the "giant in the playground" big kids often learn to control their use of force precisely because they're naturally effective. If everybody has razor sharp claws, well-honed combat reflexes and teeth that turn a bite into a one-shot killing blow...violence within a community quickly becomes extinction.
This gets reasoned into a species that is (within their own community) less violent and prone to risking conflict than animals that only do 1d3 nonlethal on unarmed attacks.
As with Weber's 'Starfire,' many such place loyalty (and essentially chivalric values) in high regard.
If we think of a timeline:
Apex Predator[AP] is Apex Predator.
AP intelligence expands.
AP-I population expands.[Apex Predator-Intelligent]
Prey populations decline.
AP-I population expands to the point where offspring cannot find their own hunting territory without guaranteed conflict.
Prey populations red-line. AP-I is not AP-Idiot, AP-I attempts to eradicate non-bloodline competitors to reduce load on Prey species in nearby territories.
Cooperation becomes obvious benefit to AP-I.
Cooperation creates (at length) and benefits from communication and regular contact.
Regular contact begets regular conflict for reasons other than inbred solitary nature. [See: humans]
Regular conflict begets regular conflict, social norms evolve to limit conflict.
[Wars, I'd expect, would be greatly fewer than our human example, simply because the last thing a naturally solitary creature would 'evolve' is the mob mentality that wars require.]
Faiths I could see being many and varied.
Religions and social organizations though, one would expect to be rare in the extreme, at least compared to humans. It is not in the nature of this solitary hunter to follow, unlike humans it's youth and natural cycle is geared to learning how to be independent[parent to self], not how to change who you're dependent upon[from parent to society/boss/bank manager]
As a result, whilst interpersonal direct relations might have more of the "I'm stronger than you" about them, they would, in my estimation, have less of the "you have established superiority and that means I kowtow."
I think Starfire gets the societal structure thing kinda set acceptably though, 'King-by-another-name:' important for overall social cohesion and internal conflict avoidance. Positions-by-merit being respected by all. (As before, the capacity for damage-by-conflict is arguably the greatest protection against said conflict) ("He would have peace ought gird for war.") and beyond those it's clan affiliation and personal reputation.
Essentially I'd see such a species as evolving into good conservatives, not making up a new code of ethics every other day, not pretending they're responsible for everything that happens everywhere etc etc.
Charity would be a personal thing, not an imposed tax.
Yanno, all good stuff :)
Important: Social evolutions only really need to happen once, if they're effective and good people or society at large seems to recognize the benefits. One might say "Species x is disinclined to this" but if it occurs once and survives, it is much faster to propagate than genetics, and unlike genetic evolutions, can be raised from the dead without any more complex a technology than oral tradition.
We have two general reasons why a solitary hunter might remain solitary after 'uplifting.' The first is that the instinctual behavioral patterns are still strong.. that is to say that there is an actual innate physiological/neurological response that is maintained in the (now) social (to some extent) creature.
The second is is potentially just as effective, and that is the sheer lack of exposure. Most animals are clumsy in new circumstances, even if the circumstance doesn't make them actively frightened or recalcitrant. Not only can this make any given social interaction awkward in and of itself, it can leave the individual with a marked distaste for repeating the experience.
Social norms arise from individuals, thoughts and feelings spread. If a mother likes a particular type of social interaction, her children will learn of it one way or another and be informed by their mothers actions and reactions. Likewise, if they see their mother rejecting any social advances, they will also be informed by this.
Say we have a species that has no problem at all with cannibalism, indeed it's their goto choice for population control and conflict resolution.
This species' society (assuming we do not subsume those more combative traits into learned behavior) could probably be given some rules.
Communication does not require close contact: Creatures whose entire psyche revolves around threat-annihilation might evolve language somehow, initially almost certainly as an outgrowth of mating rituals.
Ex: Ambush arachnid language grows out of basic & then gradually elaborated 'plucking' of another individuals web. Advanced version of this could be that individuals 'lay' a communication pipe(web construct) between hunting grounds for the primary reason, rather than ease-of-use and at-need availability.. it removes any need for other individuals to encroach on each other's territory.
You might end up with a species that is perfectly friendly so long as it can kinda fool it's 'lizard brain' (so to speak) by not actually directly sensing the individual provoking threat responses. Or one whose individuals constantly conspire in each other's destruction,
These creatures wouldn't build cities, clearly, but likewise spiders can be equally at home at ground level or at the top of a tree...and don't much care if somespideyelse makes their web above or below them.
Tool use is a really interesting problem, because the creature in some question needs not simply have the ability to make tools, but the motivation.
People often mis-characterize each other with such descriptions as "likes everything to be just so..and never change a thing." but even those who this description fits most perfectly would often LOVE a thing that helps them keep things..just so..and that equals a desire for change, albeit in narrow in scope.
The motivations of alien psyches are normally absurdly simplistic "just wants to eat" aliens that somehow find the time to travel across entire galaxies. Yanno...
"How does (and to what extent can) socialization override inborn behavioral traits"
People tend to think nowadays, despite the overwhelming scientific evidence against it..that people are much and much the same. What makes us seem more similar than we are is socialization & the shared patterns of behaviour that this creates, at least on the surface.
Then you have the question of the process of social selection, that is to say that the very existence of a social context changes the weighting of previous mate-selection criteria, the strongest, hardiest hunter might be so because he is driven to dominate, to accept no equals, which naturally will create conflict in a social context quite plausibly resulting in the relatively quick extinction of that particular heritage for the very reasons that make societies in the first place..numbers do confer a quality all of their own.