same as here. a1502 MacBook early 2015 8g i5 2.7 iris 6100 lagging when maximise window minimise , safari ,apple tv also laggy graphics. clear SMC no fixes. only 1 fix i found download [easyres] app on app store. turn off 2x retina resolution n turn on 1x any resolution. my settings are 1x 2048x1280. good desktop size n lag fix. default size is 1680x1050 with 2x retina 1 x with no laggy is 1650x1050 but vertical blank lines show. so best fit is 1x 2048x1280

Temporary solutions is download easyres app on app store and set the resolution to 2048x1280 with 1x option. Macbook A1502 Early 2015 8G 2.7 Iris 6100

Only One Fix is Download Easyres App on App Store and put Resolution to Retina 1x 2048x1280. Problem Solved. now try lagging apps, like  tv, maximise and minimise apps.........