Well, a 750M is about 1/3rd as fast as a GTX 750ti, a low end gaming GPU that you can get for around $100. And in editor performance is lower than the performance of a packaged game, and there is a slight performance hit in OSX vs Windows with UE4, that kind of performance seems expected and normal for that hardware.
You’ll have to turn down and off a lot of features to get a decent frame rate.