Can you NOT kill the squirrel? Yes, but you need talk to animals for that to happen.
Can you NOT wake up covered in blood? No. This is a important part of the DU story and it's the only scene that happens no matter what. (Alfira or dragonborn bard have to die for the DU quest to continue and the dragonborn bard despite being fully voiced is not properly implemented. She shows up in her underwear and despite Alfira being alive certain dialogue choices treat her as dead and alive at the same time)
Can you NOT have evil/dark urges? No, its the part of the origin. (but despite what some think its just dialogue choice that you can ignore and not a forced thing)
The way I see it is that DU was meant to be the main character at one point or at least a variation of DU. (some EA datamined info implied that Tav had dark urges)
Despite Larian claiming that its a mainly evil playthrough it is not, I would even go as far to say that its more enjoyable/meant to be played as a flawed individual fighting their unknown origin and becoming a 'hero'/better person (DU origin video even implies that the character is fighting against these evil thoughts and not indulging).
But if you are someone that's looking for full freedom when it comes to designing your character (backstory/class) I would say that DU is not for you.
DU gives you a lot of freedom when it comes to roleplaying but at the end of the day you are still a Bhaalspawn amnesiac.
So if you have a unique background for your playthrough/character you should stick with Tav.
