Due to design changes necessitated by model facelift between 1987 and 1994, the later models will fit the earlier ones, but the earlier ones will not fit the later models, due to the design of the grille. There is a curvature in the later headlight design that makes them incompatible with the earlier hood/grille shape.
If your car has no wipers, you can opt to get direct replacement lights without wipers. But if you'll want to install wipers, you need to get the correct Euro-light wipers that are sleeker which are more of a "__/" shape compared to the NA wipers, which are more of an "L" shape.
Vacuum control: you typically do not need it, but if you wish to install keep in mind there are differences once again between early models and facelifted models, between diesels and gasoline engine models (due to vacuum supply). If you have a wagon, the vacuum control switch is different also because of the self-leveling-system (a sedan with SLS also applies here), so that makes it 4 options for vacuum control alone. They are pretty cool when they work properly, and if you anticipate carrying heavy loads at night where the lights will point up due to the weight in the back, consider what effect this does on other drivers coming your way (they get dazzled by the glare from your lights). The vacuum control allows you to lower the beam back to the correct level to allow others to see the road, and not get dazzled.
City lights are basically park lights. In Europe and rest-of-world (ROW), the turn signals are typically not used as park lights. So a small 4W bulb is inside the main beam reflector and is activated by activating the park lights the same way. Instead of the turn signals illuminating steady, the city lights illuminate inside the headlight assembly. Some call it DRL's but they're too weak to be DRL's.
You need to use the correct 6-pin headlight wiring harness plug and move the wires around so the lights illuminate properly for the Euro assemblies. This is the time you can move the park light into the headlight to use the city light function. Others in the North American market like to use both the turn signal and city light, or just the original park light and do away with the city light. I like the city light function, it also gives the turn signals more contrast when driving at night (OFF/ON, as opposed to them going ON/BRIGHT). The standard turn signal bulb is 21W/4W, the 21W is what turns on the turn signal light, 4W is for the parking light. If you decide to use the city light, just move the wire over to the main headlight plug. If you want to place an extension instead, just place electric-tape on the contact point of the dual filament bulb to cancel out the park light.
This is how the city light looks in daylight - see how barely noticeable they are. The image with my w123 was taken with less ambient lighting, hence the city lights being more visible.
I always loved this shot, taken with just the city light illuminated.
Here's my w123 with vacuum-adjustable lights, you'll hear me clicking through the dial switch and see the light beam move up and down accordingly. This is just about 10 to 15 ft from the wall, on the road the change in beam level will be amplified.
https://www.flickr.com/photos/mbeige/15921008185/in/album-72157653462588206/