It is more an assumption theory of the fandom... Originally this game was said to be a trilogy and for some years, accomplish to have this first part with 3 possible basic endings (depending on choices) with variants according to the level of corruption Rowan have... Overlord is in essence the desire of overthrown Da Twins the fandom have, if you pay attention to the story, both are pretty unsatisfactory as leaders and most as rulers.
Besides, it's an evil path for Rowan to take as he deep more into corruption, most of the game decisions doesn't have logic or rewards if cheating (for Rowan and against him aren't active), Rowan in this path is tired, furious, dissapointed, betrayed but most importantly, with desire of revenge mixed with justice, more carefully planning his steps and with who trust with and how to do it, preparing the path and the next step in the latter.
Mainly this game have 3 possible paths (in my understanding) as for still is build as i wrote this:
1. Loyalist: boring, lil to no cheat in most scenes; specially for Alexia, as a mere human with some latent talent for magic (something that most of us are waiting, Magical Alexia), in this path Rowan's Wife makes no fucking sense to be second protagonist 'cause she's saint as fuck, having the privilege to be not touched nor molested nor raped, no nothing except, love making with her husband Rowan... WTF?! in a place as Bloodmeen in which corruption is in every corner and most slaves never have a option why the fuck for her will be any different? even if in Bloodmeen enjoy ppl giving into corruption, there's no sense for her to resist all the temptations out there in which she's exposed. The chance to get the shit done, well, it depends of what you considers is good or level of priorities, i would set 50/50 because of the complexity of the story right now (the chances for a good ending are near 0).
2. Hero: there's not much to say, it must be the most logical decisions with the corruption Rowan and his Wife have, there's a chance for them, but there's high possibility that "saving" the world will have a high cost, so, even if Da Twins are stopped and the world saved, the price will be to high, it will not end well... But heroic yes.
3. Overlord: Rowan and Alexia are split, corrupted as fuck, cheat between themselves, Alexia gives STD into all living being in Bloodmeen (no joke, she fucks everything that have a way to fuck, it doesn't matter if it have intelligence or not); Rowan is more planning, revengeful and more willing to do what is needed to have what it takes to reach his goals. If you doesn't give a fuck about ntr then you'll have a lot of fun.
Well, this are mainly 3 paths most fandom think it'll have... But there's a chance that between them, Rowan is revealed as a false hero, as the game characters always talk about Rowan's feats but most never was truly presence them, there's no a correct answer for a military with a Strategic Mind as General of renown as Rowan need to take, whatever answer Rowan gives everyone just takes as right... WTF?!... The most obvious thing is how the beginning of the game reveal Rowan's actions, and this repeats mostly in the entire game with poor to no planning. In other words, Venus Noire team can surprise us with whatever of this or more...