Powerful CPUs, Nvidia's fastest mobile GPUs, the best MiniLED or OLED screens, and a plethora of additional feats and features that are supposed to deliver the best high-end mobile gaming experience. We put the flagships from Razer, Alienware, Lenovo, Asus ROG and XMG through their paces to see what they bring to the table, and if they are worth their eyewatering sticker price.