i do see alan as being less intense about vampire hunting than edgar. vampire hunting is edgar's calling, his passion, his only purpose in life. he eats sleeps and breathes vampire hunting. he'll die on the battlefield, because he doesn't see the point in doing anything else with his life. surfboard shaping is purely for the money. if he ever became a half-vampire, he wouldn't be able to cope, not without someone else dragging him through it kicking and screaming. he'd kill himself the moment he lost hope, instead of trying to survive long term.
alan's a little more capable of adapting, imo. i like to think he took up taxidermy as a half-vampire because he'd learned about it from grandpa emerson and was genuinely interested in the craft. he's able to build a new life for himself once hunting stops being an option. he's not happy about it, and it's a very lonely, isolated existence, but he's able to take the shitty hand he's been dealt and make something bearable out of it. he's not willing to give up on life, even if it's not the life he wants. he returns to hunting not for his own sake, but for edgar's. i think he has dreams outside of hunting that fall to the wayside out of a sense of obligation to edgar, to not let him fight alone if he can help it.
the very fact that alan is a vampire in the tribe alternate endings is, imo, further proof of this. even in a situation where he's become the very monster he hates most, his relationship with his brother and best friend permanently ruined, he keeps going, whereas i think edgar is stubborn enough that even if he did make a kill, he'd immediately throw himself into the sun, regardless of how changed his post-killing morals are.
this isn't to say alan has any kind of like. fluffy bunny feelings towards vampires, he absolutely doesn't, but i don't think he has the same kind of all consuming need to spend his life fighting, and i think as he gets older he's more capable of seeing the shades of grey in things that edgar doesn't. like as a kid, yeah, he's like "oh we're gonna stake the half-vampires unprovoked? sure let's do it" but after spending years as one i think he'd have slightly more sympathy for others in that situation, at least more than edgar does.
sam is similar to alan, in his persistence. i see him as having a strong sense of justice, as well as a personal vendetta against vampires, but he also has aspirations and passions unrelated to hunting. he's able to adapt to life as a vampire, even it's not for very long, though you could absolutely argue him going after edgar in the tribe is an attempt to end his vampiric existence without having to do it himself. i think he could've thrived as a vampire were his life not cut short, especially in the universe of the tribe alternate ending where alan is also a vampire.
i guess ultimately to me edgar is someone still stuck in the black and white thinking of childhood, unable to adapt to big changes and unwilling to try. he clings to a sense of moral righteousness, because it's the only thing keeping him going. someone has to keep the vampire scourge at bay, and it might as well be him, because he has absolutely nothing else going on in his life. no strong attachments, no commitments. he never learned to make connections outside of hunting; any friendships he's engaged in are either carried by the other person (purely headcanon as we have no background on his friendship with zoe, but i do see her as being the one to initially reach out and put in the most effort in maintaining said friendship prior to getting involved in hunting) or they revolve almost entirely around vampire hunting, at least at first (sam and blake). when other people were learning how to make friends, he was studying the blade, and as an adult it remains a skill set that is out of his reach. (not to say that alan is any better at making friends because he's NOT, though his years as a half-vampire absolutely contributes at least a bit to his complete lack of friends as an adult)
