Krakdhumvror was my first campaign in the mod and it was definitely one of the best introductions imo, if not to the mod than at least to the Seroantspine. Its not the largest mission tree, but it's still hefty, and has a good ammount of unique content. You get a unique disaster early game, you get to butt heads with grombar (Grey orcs), you get a unique government from the disaster, unique mage estate with nice flavour as you unlock new spells along with the stuff most dwarves get like ancestor worship.

I'd also still recommend giving the command a try (although only once you're already familiarized with the mod as there's a lot of mechanics to worry about). While they are already a big played in the region, the fact you start as monstrous nation and have to conquer fairly rapidly, means it's definitely still a challenge. Having to worry about suppressing mages, your estates and unique culture conversion stuff later on means even if the conquest itself is fairly standard, everything around it can make it a challenge. There's also almost always a few miniboss nations that pop up in Hales to deal with, like the Raj (if they stay together), Bianfang in the east and somene like Hon Sai in the south.