The type of valves you need depends on the type of pipe-work connection you have or will have in the room or bathroom where the installation will take place.
If the pipe-work is coming out of the floor you will then need a pair of straight valves whereas if the pipe-work is coming out of the wall you will need a pair of angled valves.
If the radiator is to be a dual-use one, you will then need a pair of mixed valves (if the pipes are coming up from the floor) or angled valves (if the pipes are coming towards you from the wall).
Conventionally, chrome valves are for chrome radiators and white valves for white painted radiators.