I run FBA and when visualizing the results, I realized that some areas with lowest pFWE values are not the areas with lowest puncorrected. Does it make sense?
No, they wouldn’t be expected to match. The puncorrected values report the per-fixel p-values with no attempt to correct for multiple comparisions. In contrast, the pFWE report the p-values after correction for multiple comparisons, which involves the whole connectivity-based fixel enhancement framework, which enhance the t-values based on neighbourhood support: the higher the t-values in a given fixel’s neighbourhood, the higher the level of enhancement. So the pFWE values are not simply a scaled version of the puncorrected values. Regions with low puncorrected values may well end up with high pFWE values if they are part of a large neighbourhood where the effect is consistent – and vice versa. See the manuscript linked above for details.