Can someone outline what an evil path looks like from a storytelling perspective?
I have been wondering about this too. I picked up BG3 because I was thirsty for a good immersive sim. I am totally ok with a linear story as long as I have variety in how I deal with the problems presented to me and especially act 1 is doing a really good job in this regard.
Making the tangent a bit longer and coming from immersive sims, I really liked how the first two Dishonored games treated the "good" and "evil", low and high chaos paths, because it was treated as cause and effect. If you were careful, showed restrained and went for none violent options, you inspired the city as a whole and the NPC in particular to be less cruel as well. If you went murderhobo, otoh, the whole city would be in uproar and - with a dog-eats-dog mentality confirmed - you created a much crueler world through your actions.
I would have liked a similar approach in BG3, especially in regards to the other tapolees. You learn relatively early that all of the cultists are influenced or tadpole controlled. You can make use of the tadpole powers yourself or reject them for your own benefit, but you can't really do anything for the poor dupes under the Absolute's control. I am very glad we get to save Minthara now because no matter what you think about Drow, she didn't deserve that.
So from my point of view, making the "good" and "evil" routes more about variations within a linear storyline would be my preferred approach - characters might be on different sides depending on choice, more or less cultists (does raiding that shipment stash in Moonrise even change anything?) depending on if you tried to destroy tadpoles or not, &c. I also like it if the "good" choice isn't the fun and easy choice but maybe the mechanically harder one - which they do on several occasions. It would have been fun if the tadpoles actually corrupted you and allowed the emperor to take away some of your agency.