Why do some fighters have two engines and other have only one but still give the same performance?
Some countries don't get the most powerful engines and have to use what is available in the market. To avoid upsetting China too much, the US would not sell the F404 or the F100 to Taiwan, and a derivative of a civilian engine had to be developed.

A second reason is redundancy: When the US Navy had to decide between the F-16 and what was to become the F-18, they preferred the design with two engines, because losing your only engine over water is a much more life-threatening experience than losing it over land. Similarly, the Eurofighter was designed more for peace than for war - having two engines will reduce training losses.

Generally, a single, bigger engine will be more powerful and more efficient per unit of mass, because manufacturing tolerances will be relatively smaller in the bigger engine, if the same technology is used for both. Single engines need to have more system redundancy than one of a pair of engines, so some of that advantage cannot be transferred into the finished design. Nevertheless, from a performance standpoint the single engine fighter will look better.