Customise the shape and position of the tooltip in a scatter plot

#0: Is there a different name for the tooltip that appears on the x-axis, as opposed to the tooltip that appears near the mouse cursor?

#1: Is it possible to change the shape of the tooltip? By default it is a rectangle, with a little triangle that points towards the data point. Is it possible to remove this little triangle?

#2: By default, the tooltip on the x-axis is positioned just a little off (vertically down) from the x-axis line. This accommodates the aforementioned triangle which points up towards the data, keeping this below the axis. Is it possible to move the tooltip so that the top horizontal line of the tooltip is touching the horizontal line of the x-axis?