I have a piano trio score with more than 1200 bars and Dorico for Ipad has a hard job to manage it. It reacts very slowly and crashes sometimes. So, is this the limit to work with scores fluently on an IPad ?
There’s no specific limit on the number of bars in a project, and I would expect a modern iPad to be able to handle projects of similar scope to Dorico for macOS, all other things being equal. (The fact that Dorico for iPad will typically use less memory for samples etc. because the sounds used by default in Dorico for iPad are much more basic than those you will be using on the desktop helps a lot.)
Can you remind me of the specification of your iPad?