Start screen loads small and partially off screen

Has this only just started recently after the iOS update out of interest?

Its first occurrence was about 6-8 weeks ago. I do believe it was slightly before iOS18/iPadOS18 update. 
 

Do you think it’s worth deleting/reinstalling?

There's probably no harm in giving it a go. It is worth backing up your save file, just to be safe.

Let us know how you get on