There's afaik a rather big difference between freshly squeezed orange juice, and fruit juices that have been pasteurised. I'm not sure there's that big a difference between eating an orange and drinking the juice - other than the simple fact that the orange will contain "more stuff" that is "not sugar" than the juice - hence it'll be easier to increase sugar intake by drinking, say a litre of orange juice a day, and eating some food - rather than eating six(?) large oranges and being reasonably full.

Absolutely. I'm assuming eating an orange would have more fibre than a squeezed orange.

Buying "smooth" (no "bits") juice I would assume is missing most of the fibre.

Fructose is low GI, so there is a small insulin response only.

Ah, you are right. I think I'm misremembering. I'm basing most of what I wrote on https://www.youtube.com/watch?v=dBnniua6-oM but I watched it years ago and my memory isn't the greatest. (I also didn't fact check the video's content, so... grain of salt and all that, it does seem well sourced though)