That is not really correct.
Yes epic does handle everything as well as possible but the driver even though they provide a similar interface work rather differently. It goes as far as fundamental differences in the hardwarestructure.
No matter how well your engine runs and is optimized there will be a performance difference.
As far as a low spec computer goes… There are reasons why most developer don’t give away minimum specs early on. Because it’s not a sure thing. If you now buy a computer with your min specs and then realize you will need a bit more… Well that computer is useless. And developing on low spec computers is rather painful if you work in engine. If you have one guy for web development / back end / community stuff that works. But you don’t want to work with lower specs than you have to in any kind of graphics environment.