The biggest performance issue is going to be the browser. Because for any type of rendering performance hardware acceleration is a must. And Firefox disables that by default on Linux (needs to be manually enabled in about:config).

The second issue, which I saw based on reviews alone was a very slow camera interface.

One surprise with PinePhone optimized distros is Ubuntu Touch (ubports). Not sure what type of magic they are on, but accelerate 1080p video in the browser and fluid mobile interfaces.

Check out the Short Circuit youtube channel for their PinePhone video. Watched it expecting to see just laggy interfaces, but ubports really takes it to the next level.