To speak more to the Horde Druids and what they are or how they became a thing since since it is what I know more, I thoroughly enjoy how the races within the faction basically de-homogenized druidism. What was perceived before was it was a Night Elf only thing, and in fact Druids were going to be an Alliance only class in Classic largely out of what was shown in WC3 but as we see was scrapped for Shaman and Paladins instead, is now something for both factions and many races.
What we can say though that the class ‘druid’ as we know it is Night Elf based. Our understanding of what one is means they shapeshift, connect to the Emerald Dream, love their trees, and draw on solar and lunar powers in some way. What has happened with the rest was shoving those races, with no connections to a lot of that, into that class to make work. So what we see, historically in the lore, are not so much ‘druids’ but nature-esc users who now need to be put into a class for balance and game play.
What we’re given then is that tauren were, according to Xarataur, were among the first druids also taught by Cenarius. Given that tauren/yaungol are older than Night Elves, it can be suggested they were even the first druidic users, but perhaps not the first proper druids. Which Blizz confirmed Malfurion was. So their practices are largely in line with the Night Elves, since the practice was largely forgotten among the Kalimdor tauren and retaught by Malfurion and Cenarius to Hamuul, and then the rest of the tauren.
What differentiates, and perphas confuses, Highmountain druids is that they could have potentially kept that knowledge from pre-sundering druid practices from Cenarius and others like Xarantaur. Also being so close to Val, constant teaching was possible. They even helped turn Vydhar in Stormhiem into the eternal tree. Thats a bit above and beyond just talking to trees and caring for nature.
What we see with trolls, who also predate Night Elves, is also something completely different. We’ve seen since classic trolls able to take on different shapes of their Loa through one way or another. Since shape shifting is a key druid trait, this was taken as part reason for them given the class option though traditionally in game those trolls were priests. Mechanically that doesn’t work, of course. So what happens in Cata is the Darkspear, with the help of Vol’jin defeating Zalazane once and for all with Bwonsamdi, is them reconnecting with Gonk, Lord of the Pack and Loa of Shapes, allowing them to not fall so rigidly into single devotion to a Loa and only able to shape shift into them. The Loa of Shapes allows for them to go into Boomkin, Bear, Seal, Cat, etc without needing to devote themselves to, presumably Elune, Nalorakk, Gral, Kimbul, etc (respectively). Creating a more diverse and ‘proper’ druid to WoW mechanics.
What we see with Zandalari is kinda taking the Darkspear and cranking that up to 11. The Raptari are the druids of the Zandalari, also followers of Gonk, but use raptor forms instead. However there is nothing to say, like the Lun’ari, that “druids” can’t also be followers of Kimbul, Shadra, Akunda, really any Loa. Though as far as lore goes, they’d technically be priests or devotees. Kinda sorta do what ya want with that one. This is where the race/class combos really diverge form what we have ‘traditionally’ accepted. Though really, whats the difference between a follower of Kimbul and say, a Druid of the Claw?
Culturally speaking for each as far as classes go, shaman are more important to tauren. They’ve been the staple spiritual and knowledge keepers for the tauren. We see that with both Kalimdor and Highmountain tauren, regardless how how highly druids are held. However, druids are still held in high esteem within tauren culture as peace keepers, spiritualists, knowledge keepers, and those who can connect to nature. Things can be similarly said for priests and paladins, Seers and Sunwalkers. What is key is their relationship to the Earth Mother, An’she, Mu’sha, and the ancestors.
Trolls are a bit different. They’re held in higher regard too, but like priests and shaman, they are connected to their Loas. How that Loa is regarded is generally how that druid would be regarded. Like with the Lun’ari, mainline Zandalari say their Loa is not real. That Loa is presumably Elune. That is a cultural thing from troll tribe to troll tribe. To the Lun’ari, that could even be a little geopolitical going forward, not allowing the Night Elves’ primary deity to rise to the pantheon of Loa, especially given that history. Its quite literately heresy. Same for any druid that would be a follower of G’huun, Hir’eek or Hakkar, or even more innocent ones like bear fights between Rhunok and Nalorakk followers. To put into Night Elf terms, Druids of the Fang or Flame.
So I play a druid or two, and plenty of non-druids too. The druid I play as the the stereotypical wiseman. Knowledgeable, slow to action, avoiding conflict, tending to disputes, the works. I do, however, put a bit more of a philosophical spin on him with mild tauren supremacy twist when it comes to nature and their practices. They see others as people who could always use a helping hand. Could use a bit of guidance. While others, I assume, see him as kinda the stereotypical tree hugger.
My others, especially the more aggressive ones like Abra here, see most tauren druids as sell outs to Night Elves (see a pattern?). That for what good Hamuul did, he ultimately sold out our beliefs or allowed them to be subordinate to others. They’re too compromising. Even the Night Elf druids still fight for the Elves. What do ours do? I also just find it important to break from the traditional tauren mold. Racial stereotypes based on marginalized people are bad, yeah?
Personally, I dont see how they differ in game. They all do the same thing and they all look, generally, the same. They kinda have to too for balance. It would be nice, like we had with priests back in the day, to have race specific abilities for some classes but thats also a balancing nightmare. That a druid can really be whatever they want to be as far as roleplay goes. Do you want to be a Priest of Bethekk but abuse shapeshifting to show your devotion and piety? More power to you. Do you just want to use nature magic and RP spec into resto to be a super good farmer? Thats fun, roll with it. Were you a scout for the Zandalari or Darkspear, that was given a blessing from Paku or Hir’eek or transform into dino birds or bats to better perform your duties? Nice idea. Or are you just a traditional tauren druid, in the strictest class terms mostly defined by Night Elves? If you like it, go with it.
So personal perspective, druids are what you make of them. Have fun with it. Just keep it mildly within established lore and use mechanics to your advantage.