I’ve only been once so perhaps my info should be taken with a pinch of salt. As far as I remember the main wall is pretty consistently around 20m tall. I would think you will need a 50m rope.
Yes, the main wall is about 20m and other stuff is a bit shorter. My 50m had always been plenty there. There is some longer stuff on the horrible left (West) wall but no one does them
Here's my 70 mtrs rope after lowering off Neanderthal (5a), so I reckon that's the longest. You can try counting the quickdraws - can't remember how many it was but quite a few! Have fun.