Hover over the upper left-hand side of the table and a "square" will appear. Left-click on the square to highlight the complete table then go to the "Home" ribbon and center the table by clicking on the centering icon under the "Paragraph" section.

With reference to your "impact" request, that will take your interest to try all of the options (lines, borders, text fonts and size, et al) available. The "trial and error" process.