@Toan,
Yes. Any statistical method used in QIIME 2 is a valid statistical method, published and widely used by others. So be sure to cite each individual method you use in QIIME 2, in addition to QIIME 2, to properly credit the work of others! See here for more details on discovering tools that should be cited for individual actions in QIIME 2:
Plots are highly subjective... I find most QIIME 2 plots are easily adjusted in adobe illustrator and other image editing tools to prepare publication-ready plots. But this does not cover all possible plotting modalities! So many users (myself included) will generate finished plots in R or other software.