Using third-party scripts or "OP GUIs" in games like Roblox can lead to:
Modifies player movement (WalkSpeed and JumpPower) to traverse the open world faster.
Scripts often use StarterGui:SetCoreGuiEnabled(Enum.CoreGuiType.Backpack, false) to hide the standard Roblox inventory. OP Backpacking GUI
Custom layouts that may allow for more slots than the standard backpack. How They Are Implemented (Scripting Logic)
How to Make a Custom Backpack GUI | Roblox Scripting Tutorial Using third-party scripts or "OP GUIs" in games
A custom ScreenGui is inserted into StarterGui , containing TextLabels for data and ImageButtons for item slots.
While specific versions vary, common functionalities in these scripts often include: OP Backpacking GUI
For those interested in the technical side of how these custom GUIs are built: