Yes you're right.
I could personalize more my singing and I often do it with a live group on my back. In that kind of venues I'm free to duet with the instruments and to change the melody line too.
But I'm a 45 years old singer as hobbyst semi preofessional in small pubs, restaurant, piano bar, with backing tracks, and usually works better if we stay more close as possible to the original sound of a song.
I do it only if it comes natural not with an artificial and unnatural position of the mouth and the face.
Some friends of mine defined me chamaleontic for the way to "sound like" a lot of singer and different styles of music. And luckily it works with the customers of the pubs and bar where I sing.
But I agree with you that could be much satisfaying to be free, much more free to interpretate and sing everything...
Thanks as usual for your listening and suggest :)