Q: Can I highlight the top 5 risks plotted on the heat map?
A: Because the font is consistent for all plotted risks on the heat map, you can't use fonts or label changes to highlight the top 5 risks. However, you can configure the heat map to display only those top 5 items. See Select the Top 10 Risks to Display on the Heat Map for more information.
You can also emphasize a select number of risks by using the Size Code option in Chart Data. While it's not limited to a specific number of top risks, Size Code can be used to emphasize certain risks based on a third criteria (e.g. a total formula or residual risk). See Add a Third Criteria to the Heat Map for more information.
Q: Can I change the risk icons on the heat map (e.g. change the boxes into bubbles)?
A: Ballot is capable of showing multiple series of data on a single chart, so certain icons are reserved for each series: Series 1 is a square, Series 2 is a circle, and Series 3 is a diamond.
Though Series 1 will always display squares, you can explore additional display options through the Chart Effects and Size functions in the View menu of the scatter chart.