Its been explictly stated multiple times your going to lose friends and companions by going tadpole.
But that can happen for many other reasons as well, so it is not a true trade-off for using the tadpoles. And similarly, having a lot of friends is also separate from not using the tadpoles, so keeping one's friends is certainly not a reward/gain from not using the tadpoles. When it comes to keeping/losing one's friends and using/not using the tadpoles, those are two entirely separate things that cannot be conflated.
It's an important question for me, because I will not under any circumstances, use the tadpoles or their powers, but will be extremely angry if this choice results in Larian screwing me over on the trade-off because clearly the gains from using the powers are a very big deal. It would be especially egregious if the good/best outcomes of the game are possible to achieve only by using the tadpole powers.
I'm not sure that this is a game with a 'best' ending. It seems more like a 'best ending for you' type of game. Maybe turning into a half-mindflayer demigod is the best ending for you, or maybe removing the tadpoles, mindflayers, and absolute from the surface of the material plane is the best ending. Maybe they are all great and you should play through a couple times to see the variations.
Yes I am speaking of the best ending for me, which would exactly be never ever using the tadpoles, while at the same time removing the tadpoles and eradicating the mindflayers and the Absolute and the cult of the dead three from Faerun. Will the game provide for this outcome (and too in a reasonable way where I don't have to play the game a certain "perfect" way)? I am highly skeptical.
