Boots, PG team is very flexible at upgrades/ crossgrades, but as mentioned above it makes more sense to "go for the highest package that fits your budget"

"2. Is there a list somewhere of what instruments come with BIAB Pro 2020? I love the chorus vocals I have heard, as well as some of the drum kits, and really could like the pedal steel, mandolin and fiddle."

I will try to answer this one...

The main muscle of BIAB are Real Tracks and Real Drums. These are NOT cut out samples that you can use in samplers or such. They are actual performances by real artists that recorded content for PG Music. These were recorded very meticulously, most of them even include Shots, Holds, Pushes etc. Real Tracks work by writing out arrangement in program and they will follow chord progression and many other changes that you will/can make. There are great many Real Tracks to choose from of many genres. In my opinion, if you are into traditional music genres like Rock, Pop, Jazz, Country (and whole bunch of others) and looking to make backing tracks or original tune arrangement there is NOTHING better than BIAB as you get a lot of original content recorded by some very talented folks. They do have a lot of modern tracks too and a loop library for different flavors. But again, having said above, BIAB is not a synth.

P.S. Note of caution... PG offers 30 day money back and they stand by their word. In case (for some reason) you get lost or dislike something from first look, I suggest to come back and try it again in a day or two, do not rush to return it. This forum is active and members are very helpful. You will get most of your questions about BIAB answered within a few hours if not sooner. Also, member Pipeline (above) wrote some very cool non-official stuff to further integrate BIAB to Reaper.