Can I set my own smallest worthwhile changes to tests to improve accuracy

Yes,  you can easily customize the smallest worthwhile changes for each test by opening the test library, selecting a test and setting the appropriate 'Smallest worthwhile change' option. This process is explained here:

https://fitstats.freshdesk.com/support/solutions/articles/13000005891-how-does-the-system-interpret-smallest-worthwhile-change

You can also add up to 5 tests on the team dashboard and interpret changes using the SWC method. More information here:

https://support.en.athletemonitoring.com/support/solutions/articles/13000047663-adding-test-results-to-the-dashboard