The hinges basically control the surface alignment with the rest of the car. It should be flush and about a 1/4" gap all the way around. The striker is only adjusted horizontally to have even tightness on the weatherstripping.
You can play with the hinges but it will probably mess up your perimeter alignment. The bolts do move up and down and you can put shims behind the hinges.
It sounds like you are suffering door sag. That happens usually when the pin on the hinge or the hole the pin rides in wears out, usually egg shaped. The couple remedies is to replace the hinge or they do have aftermarket pins that are oversized and you drill their hole a little bigger. I don't know if they make them for this particular car. But you can go to a place like Advance or AutoZone and they have a Help aisle with weird parts like that. I think at Advance the packaging is called HELP. They use to be red packages. They had pins for old Ford/GM/Chrysler cars. Camaros and Firebirds were extremely bad for door sag. I replaced a many of them pins.
Make sure the door latch is functioning properly too. It might need some grease.
With a little ingenuity you can probably make one of them replacement pins work.
A wild thought, them pins are hollow on a Capri. Maybe some kind of round wedge driven inside the pin to help expand it? A screw?
There is always Roo-sport.
