The type of city and construction depends on where it was built, who built it, and for what purpose.
The big homeworlds are home to some truly massive cities. Terra has a lot of new construction, having gotten the snot bipped out of them by the Rach not too terribly long ago. Having learned the lesson, many of the cities have the types of fortifications that FPilot describes.
However, Earth's biggest defenses are in its bombardment defenses and ground-to-space weaponry. Bombardment defenses cover every single point on the planet, including the poles (as melting those off is a viable siege tactic). Ground-to-space weapons are usually in large clusters and can lance practically any fleet from the sky. Earth is a wee bit paranoid about another invasion.
Anyway, defense aside, for general city construction, think of it as today, but built up even more. There are suburbs, downtowns, rapid transit systems, etc... everything you can think of today, they've got.
As a general note, starports on most worlds are placed a fair distance from any actual habitation. Transit and transportation technology is superb and you can go 100kms in about 5 minutes on most trains. The reason for this is safety. If you think an airplane crash is bad today, a starship crash has the potential to be far worse as the superheated plasma in the drive can totally devastate a region with a 10km radius until it burns itself out.
Avalorr has some of the oldest cities in the galaxy and Adonese construction is what you'd expect from elves. Grand, sweeping structures and lots and lots of natural elements worked in. Parks everywhere and plenty of greenery. The Ritterlich by contrast are heavy into the whole macro-gothic scene. Towering monoliths and statues, lots of embossed and engraved faces, gargoyles, and statues. Castle Ravenloft on a grand scale.
Malvernians tend towards expansive structures. Imagine the Vatican but housing 25 million people and you've got your typical Malvernian city. Lots of spires, stained glass, and grand archways. Malvernians don't build 'up' so much though. They do a lot of undergound construction though.
Templars don't have a style all their own, being formed of many different races. Adonese would predominate, but anything is possible.
The Rach build spikey. If a building could be picked up and stabbed into some gigantic foe, a Rach building would serve nicely. Serrated edges, sharp points, sheer lines. Fortifications are built into practically everything.
UCOR building construction usually reflects the style of the UCOR's founding race, combined with the style of the planet the building is located on. Generally UCOR construction is what pushes the boundaries.
These are the pinnacles of construction. Less populated worlds will have the same general styles but on varying scales depending on the stage of their development. A lot of things can be prefabricated and nano-construction techniques allow for surprisingly large structres to be built in a relatively short amount of time. Many structures can be assembled in space and lifted down to a planet's surface completely intact.
For travel you've got wheels, hover, and genuine flight. All large cities have one form of mass transit or another. Flight vehicles are typically prohibited in large cities but are fine for intercity travel.
Education depends on the government/UCOR. Expect everyone to be able to read, write, do basic arithmetic, and know a thing or two about science. The closer to the core worlds you are, the more likely you are to run into people with higher education. Who receives this education is much like it is today. You need the means and time.
My .02.
--ek
