It kinda depends on the fruit tree, and the type. There’s the standard size, the dwarf size, and something in between for lots of fruit trees.
Then there’s the “columnar” trees. So you would have to know the anticipated height and diameter of the mature tree to be able to answer the question.
Usually, the catalog or instructions that come with the tree contains that info.
They’re bare-root trees that came with no instructions.
Full-size, eventually, to the best of my knowledge.
I got them from the county “Conservation District”, the woman who runs that operation suggested 8-12 feet, depending on how ambitious I intended to be in pruning.