I think there won't be any major deviations from the main ending, as in we haven't planned them. What would you like to see in the guide? Like strategies?
Not exactly too worried on the strategy front myself, though since certain unlocks of class changes or such could factor into it. But for me it is more just a few notes if there are some path/mission/quest variations or choices or relationship options that close off or open up that affect story beats or the like. I don't think we would need detailed spoilers so much as I would prefer to know the results of this choice mechanically if there is any effect as that could affect certain story beats too. Once I beat the game I tend to make one final save of my ideal route in most multi choice RPG games that I leave alone after even if I replay later. Glad to know the ending won't be too majorly different though I suspect some themes and views or even some paths to it might change for the main character to a degree. Just the fact that specific TF's or classes that arise from this choice for the MC could affect the story therefore change the overall plot in some way were part of the main issue I had. I enjoy the game play enough but sometimes even when you want a challenge you might want to go certain routes if the story shifts one way or the other.