I understand that you are seeking clarification on the appropriate MATLAB function to analyse the metric variation across the tasks.
This can be done using a Repeated Measures ANOVA test, i.e., a test for the differences in variance across matched samples in multiple groups of data. Here the groups are the tasks, and the matching is between the participants (i.e., the groups are not comprised of independent data, so a normal ANOVA test is insufficient). You should perform one of these for each metric.
Here is the MATLAB documentation for that:
