How to determine scene should be switched. Workload? framerate?

My apologies if this topic has been covered on this forum before: I tried searching for this via the search function but I wasn’t sure how to word it.

I’m creating a 2D point and click game that scrolls it’s camera with the players movement (like any standard 2D side scroller. I was wondering what if there is a quick and dirty method in checking what a suitable workload is in a scene.

For example, my game starts in a street ‘hub’ like area with many shops, sprites and animated overlays such as rain etc. I want my player to be able to ‘endlessly’ scroll right (and backtrack left) as they progress and even shops etc are visited in this view. What issues am I going to face given that there is no new ‘scene’ to load. I’m loosely aware that scene switching can be made in a way that seems invisible (to an extent) but I’m interested in knowing how I can monitor when this would be necessary.
How much I can have going on in this scene. Sprites, NPC’s, hotspots etc untill I face frame rate issues etc

That is very dependent on the hardware running it. If I were you I would pick a baseline # of objects and then test on a few devices to see the framerate, and tweak as needed. Perhaps you could detect the different platforms and OS versions and dynamically tweak that threshold.