Visualizing decision tree with feature names
hstack preserves the order of the columns, so you can piece together the feature names for each of your component arrays.  OneHotEncoder (if that's what you used) and CountVectorizer both support get_feature_names, so concatenating the lists of feature names should be possible.  To give full details would require more details about how each of the arrays was generated.  You might consider using ColumnTransformer in the future, which handles all that concatenation for you and also provides its own get_feature_names.