Keeping the hardware aside for a while, a gaming development laptop should be able to run software such as Unity, Unreal Engine, RPG Maker, Construct 2, and Stencyl without any lags or issues. Do note that, a lot of the popular games like Fortnite, PUBG, etc. are built using Unreal Engine 4.
For smooth game development make sure that the laptop you get comes with the below system recommendations.