Since you seem to be interested in multiple/double screens, MS pro can do them using 2 tablets via it's 'slave' function. 

I really want an e-ink Gvido ( https://www.gvido.tokyo) but they are outrageously expensive.   I'll probably end up getting an A4 e-ink reader like the Boox Max2 instead if the double screens music readers don't go down in price ( https://onyxboox.com/boox_max2).

 I was so tired of lugging all those notebooks around and a little embarrassed to show up at a jam with them. I cant play by ear I need a little help getting started sometime. i'm tired of having to purchase all that paper and ink. The last jam I went to almost everyone had their iPads. I decided to take the leap and ditch the paper. I found Mobile Sheets Pro I feel like a bird freed from the cage i used it out the last three times I played it feels great not to have to fumble through all that paper.  I'm putting away all my folders and notebooks. With my iPad its right here in my hand.  

I started with notebooks categorized: Christmas, Hymns, regular. Then they got too full, so I put everything in dropbox then FourScore on my Ipad. I still use a printed paper copy when I'm working on a new song. Just too easy to have it laying out than pick up my ipad and set it out.

The plan:  Everything has been scanned and saved as a PDF.  Loaded into MobileSheets (Android) and the MobileSheets library has been backed up up to Dropbox.

The reality:  Some of it like that.  Some of it in 3-ring binders.  Some of it in books.  Some of it folded inside gig bags.  Some of it sitting in a pile to the left of this keyboard waiting to be scanned (where it has sat for several years).  Some of it just a browser bookmark.  Some of it heaven knows where.

The irony is, I mostly play MD by ear.  But the stuff I've been meaning to learn and the gigbooks I don't have time to memorize and the music for club meetings... well it does accumulate, doesn't it?

I need way more than 1200 pieces of music.  The uke club alone plays more than 1200 different songs in a year of weekly meetings.  And now here come the holidays!

I use forScore on an iPad for music.  Does a ton of things and allows categorizing and sorting music in a lot of ways. It is updated pretty regularly and it’s capabilites keep expanding.  It makes gig lists, auto page turning, records etc. etc.

Started with loose leaf binders but after 100 or so pieces of paper gets way too clumsy.  Plus, collecting tab is sort of a compulsion and when you get to 1200 tunes you pretty much need an electronic collection if you plan on taking your music with you when you go places.

Do you need 1200 pieces of music?  A philosophical question!

I use a regular iPad, but a member of our group has a big iPad Pro which is the berries for visibility and readability.

Good call Skip.  What I do have is a 'cheat sheet' that has the names of the songs and their first measures.  I find it hard to remember how to start a song sometimes, when in a high noise environment with lots of other musicians playing away.

A recorder/player would be more useful with that ability I suppose. 

I just memorized a couple hundred tunes.  Not that hard,  since I play be ear.  Saves having to lug all that stuff around and spending 10 minutes looking for the tab to Happy Birthday or Mary Had A Little Lamb.

I use MobileSheets Pro on a tablet. It's for Android and Windows. I don't know that it will do all of that but it'a great for music.

Notebooks? IPad?  Help!  I have a DAAA notebook; a club Notebook in DAD.  A beginning book with paper clips and extra tunes I’m learning.  Then there is my addiction to books with lessons and others with tunes.  Argh!