I don't have any pics but you want the gaps to be even between the different panel edges.
I would have to rank replacement fiberglass as being the worst as far as out of the box fit but just like a replacement steel body panel or an original one, they all can be worked/reowrked to give a superior look.
Look at the picture posted by Tony and the back edge of the fender against the cowl looks very good but the top back edge by the door, cowl, and fender (the little triangular area) needs to flow, or be even just like the gap is between the fender side and the door and further up on the door to the cowl.
Like so many thing's it's like how much do you want to work on it. Many may never pick up on some poor fitting panels while others will. Some may be more apparent than others.
I had to do a lot of fitting on my fiberglass and steel body panels on two of my latest projects but the more I do, the more I see on an old project of mine that leaves a lot to be desired (at least to me).
If a gap is a little too loose or wide on a steel part you can add some steel to the area with a mig welder, grind it down, do some filing, and so on to get it better while on fiberglass you will be working with resin's, fiberglass matting and still use a grinder or sandpapers to get the gaps better.
Ideally you want a finished car to look like it was one piece of steel originally and then someone came back with an 1/8 or 1/4" cutter and made the door to fender opening, fenders to hood openings, doors to quarters, and so on.
Factory and replacement panel tolerances can be good or bad. It's just how much better you may want it to be.
Lighter colored cars will make poor fitting gaps more apparent while darker colors less.