if you only help the bulls, you can’t get the ‘good’ ending where you can romance both Thane and Nauxus. If you only help the bulls, then you will either take the route that involves killing Nauxus, or take the route that involves killing the doppelgänger but Nauxus will still be upset enough with you to not want to romance you.
Read the guide again, and take the paths that involve tricking both sides but also keeping Nauxus’s suspicion points below 3. This involves helping Thane a lot, but sometimes helping Nauxus. I think I did the ‘good’ route by helping Thane, sparing the lizard spy, tricking both the bulls and the lizards with the fear potion, helping Nauxus make up with the rogue lizards, and giving the apples to the lizards for the feast. I reached a point where Nauxus asked me to gather mushrooms to poison Axel, and that’s when I took Thane’s bloodied cloth and went into the painting.