One thing is for sure. Panel gaps are very important, and are one thing that can be a deciding factor if a finished vehicle is good or exceptional.
The entire process, the gaps are ignored. One of the very last steps before primer is to clean the gaps up, and squeeze filler in them to get them really dialed in. Sheets of plastic are used to put in the gaps, and filled up to. This makes an extremely consistent, even, and square gap.
Here's a great tip. Use Polypropylene plastic. Nothing sticks to it! You can squeeze filler right on it, and once the filler is dry, the plastic pops right out.