Testing a game with max graphics in Studio has a really good amount of FPS, although testing the game with the same settings in the Client has around 10-20 FPS. Why does this happen, and how can I fix it? It seems ironic that the Client, which has a lot fewer features, is more performance intensive.
The size of the window/viewport can greatly change your performance because it decides how many pixels your GPU has to update so you can see what’s going on in your game.
To see what I mean, while in Roblox Studio, grab the viewport window (cloud icon with game title) and pull it out (down toward the right right of your screen) to where it is no longer docked. Now you can resize the window to fit the entire screen.