Links
Open links sets where a link opens when you click it:
With Per link type, the rows are:
Tile Placement
Open new tiles sets where a newly opened tile goes:
With Per tile type, the rows and their defaults are:
Browser tabs have their own placement, Open browser tabs, on the Browser settings page.
Windows too narrow to show more than one tile open everything in the current pane, whatever these settings say.
Modifier Clicks
Modifier keys override these settings for one click:
For how panes, tabs and splits work, see Panels.