Both new parts are based on the Pascal architecture and use GDDR5 memory. Not a lot of details are listed on NVIDIA's specification pages, there's nothing about CUDA cores or clockspeeds.
NVIDIA claims the GeForce MX250 is up to 3.5x faster than the Intel UHD 620 integrated graphics on the Intel Core i5-8265U, while the GeForce MX230 is up to 2.6x faster than the UHD 620.