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.
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For smooth game development make sure that the laptop you get comes with the below system recommendations.