Ride height is a matter of choice by the individual.
As a point of reference in all factory drawings for 914/4, 914/6 & 914/8 (that I have been able to find) the ride height at design can be easily shown by drawing an imaginary straight line across the top of the rocker panel, extending into each wheel arch.
The centre of the wheels sit roughly on this line. With STOCK wheels and tyres. It's also worth mentioning that this is prior to any legal requirement to raise or lower the ride height to meet various countries bumper height regulations.
My car was initially sitting too low, which lead me to investigate where it should be. Haynes offer a set up measurement for the front which has been posted may times on here. I initially set my car to this but it looked a little low at the front compared to the factory blueprints. In the end I lifted the car parallel to the floor (using the imaginary line discussed above) I’m happy with the look and the ride (as its where the designers intended the car to sit, not where regulation had it finally resting and aesthetically it just looks right), but as said before, it’s personal choice.