I feel like this should be solvable on the software side, especially for medium or long distance runs. If I look at the traces, I can see that the recorded zig-zag is obviously wrong, and a bit of smoothing should be able to fix it.

Are there any running apps that are accurate?

There's nothing about geosync orbit that would help with the tree/canyon effect. Satellites directly overhead contribute the least to horizontal positioning - essentially only helping to establish the "true" clock value but not 2D position.

Multi-constellation tracking can be helpful, simply because there are more satellites to use.