In the thread you linked, 4ian’s post near the bottom gives a detailed explanation on how the engine renders.
That said, the stutter you’re having happen is irregular, so I can’t speak to why that is occurring and it is unlikely to be related to the engine itself (it would likely at a regular interval then).
However, you can always do what some other engines do in regards to scaling up the rendered resolution:
- Via scaling the physical assets and bumping up the resolution (3x size of assets, making your game 1920x1080)
or - Via the method I mention in the other thread you linked: Jerky Camera + Lerp + Low Resolution - #7 by Silver-Streak, which involves scaling up the backend native resolution by an integer factor (1x, 2x, 3x, etc), then zooming in the camera (for each layer) by that same factor.
I was tinkering around with making the 2nd option an extension, but there’s some oddness with cameras that makes it difficult to do via extensions currently.
Here’s Not-A-Vania without any changes other than resolution (and hiding the GUI to see more of the screen) and forcing the max FPS to 60 like you have in your project. Do you have the stutter still on this one? edit: Forgot to turn off a setting, https://game-previews.gdevelop-app.com/1646699558560-519267/index.html