Centering would be more a function of the theme’s template page for the content area. You can probably accomplish this by switching the post/page editor to the
Text tab and wrapping the
[connections] shortcode in a center aligned div like so:
I didn’t test this so your results may vary.
The number of columns is also entirely dependant on the content width of the theme’s page template, Tile Plus will keep adding tiles until the available width is used up and then flow to the next row. You can try to force 3-column by tweaking the tile width. If you have a responsive theme it may not be worth the effort because the page content width will change depending on the device the page is being viewed on.
By default Tile Plus will list 20 entries per page. You can disable the pagination. See this doc page for more details. A word of caution … I do not recommend disabling pagination when you have a large number because that will negatively affect the page load time for the same reasons WP limits post per page to 5 by default.
Hope that helps!