I've seen only one Capri with 18s, he had to run spacers, do a lot of cutting to make them fit. Not sure about fender rolling. He burned through wheel bearings like crazy, 17" + are very hard on wheel bearings. These are small cars made for 14/15" wheels. But there's a fair number of people running 17s. The larger the wheel the harder it is on the braking system, as well - something to keep in mind.
The cheap civic coilovers I would not bother with again, the springs were devastatingly stiff, I pulled them off and put stock parts back on.
If I had to do it again, I would buy universal sleeves from Summit Racing as well as their 2.5"ID springs. you can get them in any length & springrate and piece together your kit. (I built a custom rear suspension on my Grand Prix this way to replace a monoleaf spring)
Ground Control makes a coilover spring kit for the 88/89 323 that works pretty well, I think you can achieve 2" drop with it. It's also fairly affordable, it rides good - my only complaint is the front springs are only like 8" overall length which seems too short to me
Maybe look into a custom ground effects kit to bring the body down lower, to give the illusion the car is lower to the ground? There is one or two options out there, look into the Razzi kit