Which Arduino do I use? (and is it possible)

First I apologize if this has already been covered elsewhere in the forum. I honestly haven’t had the chance to go through everything yet.
I am looking to build a foot controller for Ableton Live. I was planning on using Live’s ability to do different things based on the keys of a computer keyboard. ie Pressing “a” launches a track, pressing ”A” does something different. I have seen posts about using these boards as keyboards so I think I’m in the right place. I was looking at the Mega 2560 Rev 3 but now I’m second guessing because I saw somewhere else on the site that it is not listed under “hardware required” section of the sample keyboard program.
Ideally this is what I want: I want one push button that will remain the same keystroke at all times. I want 8 push buttons that can be 80 different keystrokes based off of 10 different “scenes.” 2 buttons will navigate the 10 “scenes.” 1 button to advance. 1 button to go back if desired. So basically scene 1 will allow the 8 different push buttons to be keys “a”, “b”, “c”, “d”, “e”, “f”, “g”, and “h” but after one of the two “scene” buttons is pushed, the same 8 buttons can now be “r”, “3”, “&”, “C”, “4”, “H”, “9”, and “x”. In addition, I would like for it to communicate via Bluetooth w/my computer. I would also love to have a touch display on the device that would display 2 things at a time. 1) What ”scene” I am on in the form of song title. & 2) What command I last sent to Live in the form of what part of the song I last launched. ie chorus, bridge, whatever… I would LOVE these two items to named right on board via the touch screen. Like say I hit the first scene button & I can edit the name via the touch screen. I hit the 1st of the 8 buttons and I can name that command via touch screen etc…
The touch screen isn’t a must. I just thought it’d be nice to not have to keep going into the editing software to reprogram the song names. Also, the Bluetooth is just something I thought would be nice.
Everything else is pretty firm. If this is something that can be done. Thank you for your time.

Do a search for Arduino HID. There are several examples showing how people have used Arduinos to emulate a keyboard, and that seems to be the only fundamental part of your project.

There are various displays with and without their own keypads, so the display/input side is certainly possible.

I don't think you will get anywhere with the touchscreen idea, but if you're seriously interested in that side of things you might consider providing a remote web-based UI that you can access via a smartphone or tablet. It's a well-trodden path, but not something I'd recommend for your first project so you might like to keep that idea for the 'MK 2' version.