Conquistadors was a Heroes of Might & Magic clone with some quests and C&C, without mystical creatures and with limited magic.
Vikings is a full fledge RPG, the HoMM worldmap was replaced by Fallouts' one, Character development is deeper, offering more tactical options during combat and you can now craft weapons on top of traps.
Depending on your crafting level and available resources you can fine tune damage, crit. multiplier and armor piercing and there's a chance to get a small random bonus.
Combat is extremely tactical, you'll need to extensively use cover, buffs and debuffs and to control the battlefield by locking enemy archers, back-stab your enemies, stun them, use some skills against their tanks, spot and avoid traps and use your own.
Downed allies might get wounded and suffer injuries; permanent debuffs until fully healed; so you'd better excell at combat or prepare to suffer.
Quests are well designed, you're a clan leader, the storyline is close to the early Vikings serie, even some idle combat animations were taken from Floki's screenplay, quests won't have you hunting rats, they all respect the setting and your Jarl status, in the end, only the prosperity of your clan matters.
On top of this, there's a management layer, first, building your homestead, which requires resources, You can spot some while scouting during camping or while exploring a map, you can also trade or get some through quests rewards.
You also have to manage food and medicine during camping and heal wounds just like in Conquistadors.
On top of this, there's a morale mechanism, each character but the main one has 4 traits from 7 different ones plus their opposite (ex: peaceful / aggressive).
Dialog options and quests resolutions can boosts aggressive followers morale while hindering the peaceful ones and so on, i'm not a fan of this mechanism, it's a real pain, just like in Conquistador but at least, in conquistador, you could chose your followers right from the start to alleviate it.
Here, you can recruit some mercenaries from the capital but they lack character, besides, companions are very well made, good dialog, quests, idle chat, it's only second to Wizardry 8 on that regard.
TL DR
Turn-Based and party based RPG with some management mechanism done right (looking at you Owlcat), an interesting setting, good character development and quest design, great combat, a better engine would have make this a masterpiece but it's still pretty good.
Congratulations, Logic artists, If Rome fixed Viking issues (loading in and out of micro locations like houses, memory leak and engine shortcomings), it'd send Logic Artists into orbit next to SSI, Sirtech and New World Computing...