Kohanmike, I'm not sure any program that i deal with exports specifically in pixels...most of the time they export in inches (mindset to paper). That said, you can export images (screenshots) in MuseScore at specific DPI and perhaps even pixels. I'm curious what 13.3" tablet you are using. I'm using an "old" iPad Air 2 with hopes to update to the next 12.9" iPad Pro in the Spring.
To everyone else in the thread, I just took 15 minutes to download the latest version of MuseScore (2.0.3.1) and my test of a notation package is to just throw myself into it and to make it work. Please keep in mind that I do one thing that the average user doesn't do...if I can't find the answer, I look in the manual (search) and if I cannot find the answer there, I look on the web.
I was able to make the linked part easily enough...select ukulele, then add linked part, and then scroll down nearly to the end for ukulele tab. I then threw in the notes to Twinkle, Twinkle. As I mentioned before, MuseScore works from the perspective of always working with a full measure, so as you add notes, you take notes away. This is a challenge, I think, if you need to add a note between other notes...I think you often are better off deleting the contents of a measure and starting over.
The next task was to add chords...CMD + K adds chords above the notes. Spacebar toggles forward.
Then I added fretboards...there are stock guitar chords in the palette, so I selected a note and then double clicked the "C" guitar chord, placing a fretboard above the desired notes (underneath the existing chords). The fretboard DOES NOT match the existing chord, so you can end up with a printed letter and fretboard that do not match. Once the fretboard is present in the score, you can right click it and chose to customize the fretboard to the pattern you want.
My shortcut, since there is no ukulele library of fretboard shapes, was to copy the one I had just made (select and CMD + C), then to go to every other similar chord, select the note, and paste the fretboard. I copied this step for all 3 chords in the song.
The final step was to add lyrics (CMD + L), adjust the position of the "composer", and to take a screen shot.
In summary...Notion is more friendly...iOS or computer, and it costs money. I was able to create this short score in a very short amount of time (less time that it has taken to write this review), and suffice it to say that if you want to create lead sheets with MuseScore, you can do it with just a bit more effort than Notion. Interestingly, I would suggest MuseScore over Finale, which makes dealing with fretboards very difficult...MuseScore is a better option. Notion has that library of standard fretboard diagrams and by default creates a linked part--but Notion was created by guitar-friendly owners and developers.
Here's a snapshot of my score, if you are interested.
This is probably a better image (from my blog post...I generally copied and pasted what I wrote here):