Okay so the title is not the best description of what I am looking for because it probably is not an "autotune" effect but rather some sort of doubler? What I am trying to replicate is the following type of vocal chain, It feels very "narrow" to me. I am sorry the example is in Dutch, while there are probably more examples this one came to my mind.

I have tried to create a vocal chain with quite a lot of compressors, doubler, compressing the doubled signal then flattening the track and then again add compression and a doubler. The sound is getting closer but it feels a lot "weaker" and less "narrow" than the example i've provided.

Would love to hear some suggestions I can try out to make it closer!

 

i'm not sure about the signal chain. But i definitely hear some heavy auto-tune.
You could also try a really short slap-back delay for thickening your vocals like they did in this song.