The intercity coaches generally ( depending on the operator) will have a toilet on board, but they all do have stops at fixed places for the passengers to get out, walk around and take care of that. However, the feature that differentiates a bus as short distance or long distance is the final drive ratio, as the city route buses are geared for best fuel economy at low speeds, and at highway speeds the fuel consumption is a lot higher than when in inner city streets with start stop traffic. The long distance buses ( often called a coach as well) are more optimised for best fuel economy at the rated speed limit on long roads, where they spend most of the time.
As an aside German tour buses are designed to have best fuel economy on an Autobahn at 140kph, and any bus that does not have that is almost automatically designated as a city bus, even if it is capable of Autobahn travel at 120kph, though there the engine will be operating well out of the green band of optimal revs and fuel consumption.
Here in south Africa the most common bus is a minibus, originally a Toyota E20, of which there are still a lot around, though now the standard is a Toyota Quantum, with a smattering of other Toyota 16 seaters around, a few Nissan 16 seaters, a number of MB sprinter van conversions, and the odd GWM and other Chinese "upside down toyota' copies. Then you get actual buses, almost all of them being 65 seaters, mostly Marcopolo, MB, Iveco, Scania and even a few VW ones. The city buses range from Leylands from 1970, all the way to luxury coaches that are assembled locally from a Brazilian made chassis.
There are 2 double decker buses around, old Leyland powered buses ( think old London double decker buses from the 1970's) used as tourist buses. They come past me every day in holiday season, and every weekend as well, with a cut off top to expose the passengers to the view. They had to put a cage there after an unfortunate accident involving a drunk passenger and a tree.