As a quick test, I did try this using the Tilemap platformer example:
Resolution set to 160x90 in the game properties.
Game resolution set to 1280x720 via events (window not resized)
Zoom set to 8x (8x90=720)
Framerate minimum set to 60 fps, max 120fps
Camera lerped to player location
Overall it seems pretty smooth to me, and these are the only events needed to accomplish it:
To try it out yourself you can check the preview here: https://game-previews.gdevelop-app.com/1644180077522-554647/index.html
You’ll want to hit F11 after launching the preview to full-screen it.
Here’s the same example without doing the resolution change:
https://game-previews.gdevelop-app.com/1644180494084-788199/index.html