I got to try the purism librem and it was snappy and responsive. touchscreen input was fluid. I didn't try a lot of apps.

In comparison I saw some pine videos and every one seemed to be laggy and stuttery right at the main screen

I'm uncertain the root cause of this.

It could be hardware performance, but I would guess that's not all of it. It might be performance tuning.

I think apple does really good tuning on their hardware. The reason everyone senses apple is good/solid is because they've tuned the UI to be very responsive. It doesn't mean apple stuff will execute an app faster, it means that the touchscreen input and graphical output are highly linked/tuned. I think it's designed in.

I think that's probably the key to all of this. Put the touchscreen and the graphics in the same library, and dispatch to the app while preventing it from impacting the feedback loop. Then it won't matter that you have a slower phone or that your app is a script instead of compiled.