I've already said which software I use on the iPad, and posted the video where I tested it. That's a good place to start with, it's free and does what you need. Here: https://www.youtube.com/watch?v=pCldXEMOCLM
Maybe someone else will come in here and say what they recommend.
I think there are a couple of other apps at the App store, you could try one of those. But Stop Motion Studio did all I needed it to do.
If you shoot at 12 fps, or at 15 fps, you shoot on ones. You don't want less than 12 moves per second.
Yes. I imported my animation from the iPad into After Effects to do the greenscreen keying.
I shot my animation with Stop Motion Studio on the iPad. The app saves a movie file to the Photo Album in the iPad. It was 1920 x 1080 HD resolution.
Then I connected the iPad to my Mac computer with the USB/charge cable, and used an app on the Mac called Image Capture, which lets me see all the photos and videos in my Photo Album on the iPad, and move them over to the computer.
Because you are using a Windows PC, I don't know what program you would use to copy your video file from the iPad to the computer, but I'm sure there are some. Lots of people use iPads and Windows computers so they would need to do that. ...Will just google "transfer from iPad to PC"... Ok, it looks like the most common solution is to copy files from iPad to iTunes, then to your PC. But here is one page that explains how to transfer directly to a PC without iTunes, using their software: https://www.imobie.com/support/transfer-files-from-ipad-to-pc.htm You can look for your own solutions, I haven't tried this and can't vouch for it.
Once the movie file was in a folder on my computer, I opened After Effects CS5 and imported the mov file. I can also import it into other programs I use like TV Paint or my editing program, but I needed to key out the green first and AE does that better than anything else that I have. So then I keyed out the green background using a built-in AE tool called Keylight. (Won't go into details here, but there are tutorials on Youtube for this.) Then I saved a new mov file.