Wow, that is a lot of questions.

I can start, and in reverse order:

#5 I upgraded from Melodyne Assistant V4 to Assistant V5 and I don't regret it for a minute, the workflow continues to improve with each version and the new chord feature is a welcome addition. There were very good sale prices several months back. Don't know if they are still on.

#4 Melodyne in Reaper is full ARA meaning it is a pleasure to work with. While I have used the standalone version in the past for editing (prior to ARA there were times when it was necessary cause in early days it was at times buggy in the DAW). However, in resent years I use it exclusively in Reaper. I have never recorded into the Standalone - never a reason to do that.

#3 I always first go to Sweetwater if it is available there. Highly recommend this vendor. I got my V5 upgrade there.

#2 Can't say much about this as this is not what I use it for. In my case I only tweek my vocals to fix the bad notes I sing. For this there is nothing better except to sing the correct notes to begin with.

#1 Much much easier to work with. I am sure there may be some features which I wish I understood better, but for the most part it was plug and play for me.

Dan, BIAB2024, SoundCloud Win11, i7(12thGen), 32GB, 1TB SSD(M.2 NVMe SSD), 2TB Libraries, 1 TB(WD-Black), 2TB SSD(M.2 NVMe SSD)Data, Motu Audio Express, Keystation 61, SL88 Studio, Reaper