I am running Blender 2.8 2019-04-30 hash e8daa615704b and it is very hard to see selected vertices & edges in edit mode. In the attached image the left and top edges on the forward face are selected, and if I look very closely I cna see that, but it is not nearly as easy to see as it was in 2.79 or in videos I have seen of 2.80. I also had the same result with an earlier version (f32902e6dacf) from on or about 2019-04-23.
Is there a preference I can set to make this more visible? I understand this is beta software and I may just have to wait. If it isn't controllable via a preference value then I will look to see if a bug has been filed.