Dear, In SEM, if you are using AMOS, which has the data related assumptions (namely, minimum data size, and normality). In AMOS, you need to fulfill the condition of the data for each group before running analysis. There are different criteria (ratio with the number of items/observed variables, you may find some relevant literature for minimum sample size). However in PLS based SEM i.e. using SmartPLS, there is no data related assumptions (i.e., minimum data sample and normality assumption).

In nutshell, for PLS based analysis using SmartPLS you can safely run the analysis, however, for CB based SEM you need to fulfill the data assumptions.