I also have a spare iPad mini 2 that I run IF on (although it’s just 16GB!). Typically the game will crash due to the memory filling up. The best thing to do is delete all your replays and other apps while operating on the lowest tolerable settings.
Since the graphics update in 19.1 there hasn’t really been a graphics option that results in acceptance looks/performance for the iPad mini 2. It’s a complicated issue but essentially it comes down to the fact that screen resolution is tied to the other graphics parameters, whereas before 19.1 it was an independent setting. Resolution was also changed to be a fixed pixel number and no longer a % of the screen pixels. In short, these factors hurt older devices with larger screens (such as ours).
I’ve been in contact with staff about this over the past few months and yesterday they informed me the next update will make resolution an independent setting again! This should help a lot with your current issue, lmk if you have any questions