Link Aggregation only helps if you are 1) looking for redundancy 2) are transfer multiple individual streams of data. Packets of data aren’t split, instead they are sent to one port or the other based on algorithm.

The accuracy varies a lot from my experience. Both my buddy and I do a lot of mountain biking together. Separately he runs and while I mostly walk. We have both found that they can be off by 10-20% compared to our Garmin bike trackers on the trails and comparing our distances side by side. We have also both found them to be off by 10% or so with walking/running. This has been an open discussion since the Series 2 days and we have both upgraded regularly hoping the better processors would fix the issues. He even got an Ultra last year and it hasn’t proven to be much better.