Facet
EuiFacetButtons are to be used when allowing lists with multiple search params to be filtered down by these particular params. They allow for an icon node and/or quantity to be passed. You can also indicate the current selection with isSelected. Other props include isDisabled and isLoading (which will swap the quantity indicator with a loading icon).
Facet layout
Typically, each facet grouping should display similarly. For example, they should all have icons or be similar icon nodes (like avatars). It is up to you whether each group should be single or multi-selection.
Utilize the EuiFacetGroup wrapper to correctly layout multiple facets. You can supply a layout of either horizontal or vertical with the default being vertical. Be sure to contain vertical layouts in a skinny component or give it a max-width.