Screen width on multiple devices

Yes, that's the approach to deal with different devices. Also note: if you use pictures in your songs, the Picture Size setting in the "Song Display" settings is your friend.

I have a standard "reference" song with the maximum line length and biggest pictures I use in my sets. I make absolutely sure that none of my songs gets wider than this song. Simple approach: I use LivePrompter 2 on Windows, load my "reference" song and resize the LivePrompter window until the text lines and pictures fit inside the window width. Then I am sure that the window size is set up correctly - now when I create a new song file, I can check it directly on that LP 2 installation on my desktop - now I know this song will fit inside my standard width. If it doesn't, I'll put in line breaks to make sure it fits. And since I'm doing my editing on the same PC that this "check" installation runs on, the workflow is pretty straightforward without the need to sync - the desktop version directly loads the file I'm editing.

For any new device format, I load that "reference" song and calibrate the Text Size and Picture Size settings so that the reference song fits on the device screen width - done!